/
activerecord_validations_callbacks.html
593 lines (540 loc) · 34.9 KB
/
activerecord_validations_callbacks.html
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" lang="en" xml:lang="en">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
<title>Active Record Validations and Callbacks</title>
<!--[if lt IE 8]>
<script src="http://ie7-js.googlecode.com/svn/version/2.0(beta3)/IE8.js" type="text/javascript"></script>
<![endif]-->
<link href="stylesheets/base.css" media="screen" rel="Stylesheet" type="text/css" />
<link href="stylesheets/forms.css" media="screen" rel="Stylesheet" type="text/css" />
<link href="stylesheets/more.css" media="screen" rel="Stylesheet" type="text/css" />
<style type="text/css">
div#container {
max-width: 900px;
padding-bottom: 3em;
}
div#content {
margin-left: 200px;
}
div#container.notoc {
max-width: 600px;
}
.notoc div#content {
margin-left: 0;
}
pre {
line-height: 1.4em;
}
#content p tt {
background: #eeeeee;
border: solid 1px #cccccc;
padding: 3px;
}
dt {
font-weight: bold;
}
#content dt tt {
font-size: 10pt;
}
dd {
margin-left: 3em;
}
#content dt tt, #content pre tt {
background: none;
padding: 0;
border: 0;
}
#content .olist ol {
margin-left: 2em;
}
#header {
position: relative;
max-width: 840px;
margin-left: auto;
margin-right: auto;
}
#header.notoc {
max-width: 580px;
}
#logo {
position: absolute;
left: 10px;
top: 10px;
width: 110px;
height: 140px;
}
div#header h1#site_title {
background: url('images/ruby_on_rails_by_mike_rundle2.gif') top left no-repeat;
position: absolute;
width: 392px;
height: 55px;
left: 145px;
top: 20px;
margin: 0;
padding: 0;
}
#site_title span {
display: none;
}
#site_title_tagline {
display: none;
}
ul#navMain {
position: absolute;
margin: 0;
padding: 0;
top: 97px;
left: 145px;
}
.left-floaty, .right-floaty {
padding: 15px;
}
.admonitionblock,
.tableblock {
margin-left: 1em;
margin-right: 1em;
margin-top: 0.25em;
margin-bottom: 1em;
}
.admonitionblock .icon {
padding-right: 8px;
}
.admonitionblock .content {
border: solid 1px #ffda78;
background: #fffebd;
padding: 10px;
padding-top: 8px;
padding-bottom: 8px;
}
.admonitionblock .title {
font-size: 140%;
margin-bottom: 0.5em;
}
.tableblock table {
border: solid 1px #aaaaff;
background: #f0f0ff;
}
.tableblock th {
background: #e0e0e0;
}
.tableblock th,
.tableblock td {
padding: 3px;
padding-left: 5px;
padding-right: 5px;
}
.sidebarblock {
margin-top: 0.25em;
margin: 1em;
border: solid 1px #ccccbb;
padding: 8px;
background: #ffffe0;
}
.sidebarblock .sidebar-title {
font-size: 140%;
font-weight: 600;
margin-bottom: 0.3em;
}
.sidebarblock .sidebar-content > .para:last-child > p {
margin-bottom: 0;
}
.sidebarblock .sidebar-title a {
text-decoration: none;
}
.sidebarblock .sidebar-title a:hover {
text-decoration: underline;
}
</style>
</head>
<body>
<div id="header" >
<div id="logo">
<a href="index.html" title="Ruby on Rails"><img src="images/rails_logo_remix.gif" alt="Rails" height="140" width="110" /></a>
</div>
<h1 id="site_title"><span>Ruby on Rails</span></h1>
<h2 id="site_title_tagline">Sustainable productivity for web-application development</h2>
<ul id="navMain">
<li class="first-child"><a href="http://www.rubyonrails.org/" title="Ruby on Rails" class="ruby_on_rails">Ruby on Rails</a></li>
<li><a class="manuals" href="index.html" title="Manuals Index">Guides Index</a></li>
</ul>
</div>
<div id="container">
<div id="sidebar">
<h2>Chapters</h2>
<ol>
<li>
<a href="#_motivations_to_validate_your_active_record_objects">Motivations to validate your Active Record objects</a>
</li>
<li>
<a href="#_how_it_works">How it works</a>
<ul>
<li><a href="#_when_does_validation_happens">When does validation happens?</a></li>
<li><a href="#_the_meaning_of_em_valid_em">The meaning of <em>valid</em></a></li>
</ul>
</li>
<li>
<a href="#_the_declarative_validation_helpers">The declarative validation helpers</a>
<ul>
<li><a href="#_the_tt_validates_acceptance_of_tt_helper">The <tt>validates_acceptance_of</tt> helper</a></li>
<li><a href="#_the_tt_validates_associated_tt_helper">The <tt>validates_associated</tt> helper</a></li>
<li><a href="#_the_tt_validates_confirmation_of_tt_helper">The <tt>validates_confirmation_of</tt> helper</a></li>
<li><a href="#_the_tt_validates_each_tt_helper">The <tt>validates_each</tt> helper</a></li>
<li><a href="#_the_tt_validates_exclusion_of_tt_helper">The <tt>validates_exclusion_of</tt> helper</a></li>
<li><a href="#_the_tt_validates_format_of_tt_helper">The <tt>validates_format_of</tt> helper</a></li>
<li><a href="#_the_tt_validates_inclusion_of_tt_helper">The <tt>validates_inclusion_of</tt> helper</a></li>
<li><a href="#_the_tt_validates_length_of_tt_helper">The <tt>validates_length_of</tt> helper</a></li>
<li><a href="#_the_tt_validates_numericallity_of_tt_helper">The <tt>validates_numericallity_of</tt> helper</a></li>
<li><a href="#_the_tt_validates_presence_of_tt_helper">The <tt>validates_presence_of</tt> helper</a></li>
<li><a href="#_the_tt_validates_size_of_tt_helper">The <tt>validates_size_of</tt> helper</a></li>
<li><a href="#_the_validates_uniqueness_of_helper">The validates_uniqueness_of+ helper</a></li>
</ul>
</li>
<li>
<a href="#_common_validation_options">Common validation options</a>
</li>
<li>
<a href="#_changelog">Changelog</a>
</li>
</ol>
</div>
<div id="content">
<h1>Active Record Validations and Callbacks</h1>
<div id="preamble">
<div class="sectionbody">
<div class="para"><p>This guide teaches you how to work with the lifecycle of your Active Record objects. More precisely, you will learn how to validate the state of your objects before they go into the database and also how to teach them to perform custom operations at certain points of their lifecycles.</p></div>
<div class="para"><p>After reading this guide and trying out the presented concepts, we hope that you'll be able to:</p></div>
<div class="ilist"><ul>
<li>
<p>
Correctly use all the built-in Active Record validation helpers
</p>
</li>
<li>
<p>
Create your own custom validation methods
</p>
</li>
<li>
<p>
Work with the error messages generated by the validation proccess
</p>
</li>
<li>
<p>
Register callback methods that will execute custom operations during your objects lifecycle, for example before/after they are saved.
</p>
</li>
<li>
<p>
Create special classes that encapsulate common behaviour for your callbacks
</p>
</li>
<li>
<p>
Create Observers - classes with callback methods specific for each of your models, keeping the callback code outside your models' declarations.
</p>
</li>
</ul></div>
</div>
</div>
<h2 id="_motivations_to_validate_your_active_record_objects">1. Motivations to validate your Active Record objects</h2>
<div class="sectionbody">
<div class="para"><p>The main reason for validating your objects before they get into the database is to ensure that only valid data is recorded. It's important to be sure that an email address column only contains valid email addresses, or that the customer's name column will never be empty. Constraints like that keep your database organized and helps your application to work properly.</p></div>
<div class="para"><p>There are several ways to validate the data that goes to the database, like using database native constraints, implementing validations only at the client side or implementing them directly into your models. Each one has pros and cons:</p></div>
<div class="ilist"><ul>
<li>
<p>
Using database constraints and/or stored procedures makes the validation mechanisms database-dependent and may turn your application into a hard to test and mantain beast. However, if your database is used by other applications, it may be a good idea to use some constraints also at the database level.
</p>
</li>
<li>
<p>
Implementing validations only at the client side can be problematic, specially with web-based applications. Usually this kind of validation is done using javascript, which may be turned off in the user's browser, leading to invalid data getting inside your database. However, if combined with server side validation, client side validation may be useful, since the user can have a faster feedback from the application when trying to save invalid data.
</p>
</li>
<li>
<p>
Using validation directly into your Active Record classes ensures that only valid data gets recorded, while still keeping the validation code in the right place, avoiding breaking the MVC pattern. Since the validation happens on the server side, the user cannot disable it, so it's also safer. It may be a hard and tedious work to implement some of the logic involved in your models' validations, but fear not: Active Record gives you the hability to easily create validations, using several built-in helpers while still allowing you to create your own validation methods.
</p>
</li>
</ul></div>
</div>
<h2 id="_how_it_works">2. How it works</h2>
<div class="sectionbody">
<h3 id="_when_does_validation_happens">2.1. When does validation happens?</h3>
<div class="para"><p>There are two kinds of Active Record objects: those that correspond to a row inside your database and those who do not. When you create a fresh object, using the <tt>new</tt> method, that object does not belong to the database yet. Once you call <tt>save</tt> upon that object it'll be recorded to it's table. Active Record uses the <tt>new_record?</tt> instance method to discover if an object is already in the database or not. Consider the following simple and very creative Active Record class:</p></div>
<div class="listingblock">
<div class="content"><!-- Generator: GNU source-highlight 2.9
by Lorenzo Bettini
http://www.lorenzobettini.it
http://www.gnu.org/software/src-highlite -->
<pre><tt><span style="font-weight: bold"><span style="color: #0000FF">class</span></span> Person <span style="color: #990000"><</span> ActiveRecord<span style="color: #990000">::</span>Base
<span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
</tt></pre></div></div>
<div class="para"><p>We can see how it works by looking at the following script/console output:</p></div>
<div class="listingblock">
<div class="content">
<pre><tt>>> p = Person.new(:name => "John Doe", :birthdate => Date.parse("09/03/1979"))
=> #<Person id: nil, name: "John Doe", birthdate: "1979-09-03", created_at: nil, updated_at: nil>
>> p.new_record?
=> true
>> p.save
=> true
>> p.new_record?
=> false</tt></pre>
</div></div>
<div class="para"><p>Saving new records means sending an SQL insert operation to the database, while saving existing records (by calling either <tt>save</tt>, <tt>update_attribute</tt> or <tt>update_attributes</tt>) will result in a SQL update operation. Active Record will use this facts to perform validations upon your objects, avoiding then to be recorded to the database if their inner state is invalid in some way. You can specify validations that will be beformed every time a object is saved, just when you're creating a new record or when you're updating an existing one.</p></div>
<h3 id="_the_meaning_of_em_valid_em">2.2. The meaning of <em>valid</em></h3>
<div class="para"><p>For verifying if an object is valid, Active Record uses the <tt>valid?</tt> method, which basically looks inside the object to see if it has any validation errors. These errors live in a collection that can be accessed through the <tt>errors</tt> instance method. The proccess is really simple: If the <tt>errors</tt> method returns an empty collection, the object is valid and can be saved. Each time a validation fails, an error message is added to the <tt>errors</tt> collection.</p></div>
</div>
<h2 id="_the_declarative_validation_helpers">3. The declarative validation helpers</h2>
<div class="sectionbody">
<div class="para"><p>Active Record offers many pre-defined validation helpers that you can use directly inside your class definitions. These helpers create validations rules that are commonly used in most of the applications that you'll write, so you don't need to recreate it everytime, avoiding code duplication, keeping everything organized and boosting your productivity. Everytime a validation fails, an error message is added to the object's <tt>errors</tt> collection, this message being associated with the field being validated.</p></div>
<div class="para"><p>Each helper accepts an arbitrary number of attributes, received as symbols, so with a single line of code you can add the same kind of validation to several attributes.</p></div>
<div class="para"><p>All these helpers accept the <tt>:on</tt> and <tt>:message</tt> options, which define when the validation should be applied and what message should be added to the <tt>errors</tt> collection when it fails, respectively. The <tt>:on</tt> option takes one the values <tt>:save</tt> (it's the default), <tt>:create</tt> or <tt>:update</tt>. There is a default error message for each one of the validation helpers. These messages are used when the <tt>:message</tt> option isn't used. Let's take a look at each one of the available helpers, listed in alphabetic order.</p></div>
<h3 id="_the_tt_validates_acceptance_of_tt_helper">3.1. The <tt>validates_acceptance_of</tt> helper</h3>
<div class="para"><p>Validates that a checkbox has been checked for agreement purposes. It's normally used when the user needs to agree with your application's terms of service, confirm reading some clauses or any similar concept. This validation is very specific to web applications and actually this <em>acceptance</em> does not need to be recorded anywhere in your database (if you don't have a field for it, the helper will just create a virtual attribute).</p></div>
<div class="listingblock">
<div class="content"><!-- Generator: GNU source-highlight 2.9
by Lorenzo Bettini
http://www.lorenzobettini.it
http://www.gnu.org/software/src-highlite -->
<pre><tt><span style="font-weight: bold"><span style="color: #0000FF">class</span></span> Person <span style="color: #990000"><</span> ActiveRecord<span style="color: #990000">::</span>Base
validates_acceptance_of <span style="color: #990000">:</span>terms_of_service
<span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
</tt></pre></div></div>
<div class="para"><p>The default error message for <tt>validates_acceptance_of</tt> is "<em>must be accepted</em>"</p></div>
<div class="para"><p><tt>validates_acceptance_of</tt> can receive an <tt>:accept</tt> option, which determines the value that will be considered acceptance. It defaults to "1", but you can change it.</p></div>
<div class="listingblock">
<div class="content"><!-- Generator: GNU source-highlight 2.9
by Lorenzo Bettini
http://www.lorenzobettini.it
http://www.gnu.org/software/src-highlite -->
<pre><tt><span style="font-weight: bold"><span style="color: #0000FF">class</span></span> Person <span style="color: #990000"><</span> ActiveRecord<span style="color: #990000">::</span>Base
validates_acceptance_of <span style="color: #990000">:</span>terms_of_service<span style="color: #990000">,</span> <span style="color: #990000">:</span>accept <span style="color: #990000">=></span> <span style="color: #FF0000">'yes'</span>
<span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
</tt></pre></div></div>
<h3 id="_the_tt_validates_associated_tt_helper">3.2. The <tt>validates_associated</tt> helper</h3>
<div class="para"><p>You should use this helper when your model has associations with other models and they also need to be validated. When you try to save your object, <tt>valid?</tt> will be called upon each one of the associated objects.</p></div>
<div class="listingblock">
<div class="content"><!-- Generator: GNU source-highlight 2.9
by Lorenzo Bettini
http://www.lorenzobettini.it
http://www.gnu.org/software/src-highlite -->
<pre><tt><span style="font-weight: bold"><span style="color: #0000FF">class</span></span> Library <span style="color: #990000"><</span> ActiveRecord<span style="color: #990000">::</span>Base
has_many <span style="color: #990000">:</span>books
validates_associated <span style="color: #990000">:</span>books
<span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
</tt></pre></div></div>
<div class="para"><p>This validation will work with all the association types.</p></div>
<div class="admonitionblock">
<table><tr>
<td class="icon">
<img src="./images/icons/caution.png" alt="Caution" />
</td>
<td class="content">Pay attention not to use <tt>validates_associated</tt> on both ends of your associations, because this will lead to several recursive calls and blow up the method calls' stack.</td>
</tr></table>
</div>
<div class="para"><p>The default error message for <tt>validates_associated</tt> is "<em>is invalid</em>". Note that the errors for each failed validation in the associated objects will be set there and not in this model.</p></div>
<h3 id="_the_tt_validates_confirmation_of_tt_helper">3.3. The <tt>validates_confirmation_of</tt> helper</h3>
<div class="para"><p>You should use this helper when you have two text fields that should receive exactly the same content, like when you want to confirm an email address or password. This validation creates a virtual attribute, using the name of the field that has to be confirmed with <em>_confirmation</em> appended.</p></div>
<div class="listingblock">
<div class="content"><!-- Generator: GNU source-highlight 2.9
by Lorenzo Bettini
http://www.lorenzobettini.it
http://www.gnu.org/software/src-highlite -->
<pre><tt><span style="font-weight: bold"><span style="color: #0000FF">class</span></span> Person <span style="color: #990000"><</span> ActiveRecord<span style="color: #990000">::</span>Base
validates_confirmation_of <span style="color: #990000">:</span>email
<span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
</tt></pre></div></div>
<div class="para"><p>In your view template you could use something like</p></div>
<div class="listingblock">
<div class="content">
<pre><tt><%= text_field :person, :email %>
<%= text_field :person, :email_confirmation %></tt></pre>
</div></div>
<div class="admonitionblock">
<table><tr>
<td class="icon">
<img src="./images/icons/note.png" alt="Note" />
</td>
<td class="content">This check is performed only if <tt>email_confirmation</tt> is not nil, and by default only on save. To require confirmation, make sure to add a presence check for the confirmation attribute (we'll take a look at <tt>validates_presence_of</tt> later on this guide):</td>
</tr></table>
</div>
<div class="listingblock">
<div class="content"><!-- Generator: GNU source-highlight 2.9
by Lorenzo Bettini
http://www.lorenzobettini.it
http://www.gnu.org/software/src-highlite -->
<pre><tt><span style="font-weight: bold"><span style="color: #0000FF">class</span></span> Person <span style="color: #990000"><</span> ActiveRecord<span style="color: #990000">::</span>Base
validates_confirmation_of <span style="color: #990000">:</span>email
validates_presence_of <span style="color: #990000">:</span>email_confirmation
<span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
</tt></pre></div></div>
<div class="para"><p>The default error message for <tt>validates_confirmation_of</tt> is "<em>doesn't match confirmation</em>"</p></div>
<h3 id="_the_tt_validates_each_tt_helper">3.4. The <tt>validates_each</tt> helper</h3>
<div class="para"><p>This helper validates attributes against a block. It doesn't have a predefined validation function. You should create one using a block, and every attribute passed to <tt>validates_each</tt> will be tested against it. In the following example, we don't want names and surnames to begin with lower case.</p></div>
<div class="listingblock">
<div class="content"><!-- Generator: GNU source-highlight 2.9
by Lorenzo Bettini
http://www.lorenzobettini.it
http://www.gnu.org/software/src-highlite -->
<pre><tt><span style="font-weight: bold"><span style="color: #0000FF">class</span></span> Person <span style="color: #990000"><</span> ActiveRecord<span style="color: #990000">::</span>Base
validates_each <span style="color: #990000">:</span>name<span style="color: #990000">,</span> <span style="color: #990000">:</span>surname <span style="font-weight: bold"><span style="color: #0000FF">do</span></span> <span style="color: #990000">|</span>model<span style="color: #990000">,</span> attr<span style="color: #990000">,</span> value<span style="color: #990000">|</span>
model<span style="color: #990000">.</span>errors<span style="color: #990000">.</span>add<span style="color: #990000">(</span>attr<span style="color: #990000">,</span> <span style="color: #FF0000">'Must start with upper case'</span><span style="color: #990000">)</span> <span style="font-weight: bold"><span style="color: #0000FF">if</span></span> value <span style="color: #990000">=~</span> <span style="color: #FF6600">/^[a-z]/</span>
<span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
<span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
</tt></pre></div></div>
<div class="para"><p>The block receives the model, the attribute's name and the attribute's value. If your validation fails, you can add an error message to the model, therefore making it invalid.</p></div>
<h3 id="_the_tt_validates_exclusion_of_tt_helper">3.5. The <tt>validates_exclusion_of</tt> helper</h3>
<div class="para"><p>This helper validates that the attributes' values are not included in a given set. In fact, this set can be any enumerable object.</p></div>
<div class="listingblock">
<div class="content"><!-- Generator: GNU source-highlight 2.9
by Lorenzo Bettini
http://www.lorenzobettini.it
http://www.gnu.org/software/src-highlite -->
<pre><tt><span style="font-weight: bold"><span style="color: #0000FF">class</span></span> MovieFile <span style="color: #990000"><</span> ActiveRecord<span style="color: #990000">::</span>Base
validates_exclusion_of <span style="color: #990000">:</span>format<span style="color: #990000">,</span> <span style="color: #990000">:</span><span style="font-weight: bold"><span style="color: #0000FF">in</span></span> <span style="color: #990000">=></span> <span style="color: #990000">%</span>w<span style="color: #990000">(</span>mov avi<span style="color: #990000">),</span> <span style="color: #990000">:</span>message <span style="color: #990000">=></span> <span style="color: #FF0000">"Extension %s is not allowed"</span>
<span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
</tt></pre></div></div>
<div class="para"><p>The <tt>validates_exclusion_of</tt> helper has an option <tt>:in</tt> that receives the set of values that will not be accepted for the validated attributes. The <tt>:in</tt> option has an alias called <tt>:within</tt> that you can use for the same purpose, if you'd like to. In the previous example we used the <tt>:message</tt> option to show how we can personalize it with the current attribute's value, through the <tt>%s</tt> format mask.</p></div>
<div class="para"><p>The default error message for <tt>validates_exclusion_of</tt> is "<em>is not included in the list</em>".</p></div>
<h3 id="_the_tt_validates_format_of_tt_helper">3.6. The <tt>validates_format_of</tt> helper</h3>
<div class="para"><p>This helper validates the attributes's values by testing if they match a given pattern. This pattern must be specified using a Ruby regular expression, which must be passed through the <tt>:with</tt> option.</p></div>
<div class="listingblock">
<div class="content"><!-- Generator: GNU source-highlight 2.9
by Lorenzo Bettini
http://www.lorenzobettini.it
http://www.gnu.org/software/src-highlite -->
<pre><tt><span style="font-weight: bold"><span style="color: #0000FF">class</span></span> Product <span style="color: #990000"><</span> ActiveRecord<span style="color: #990000">::</span>Base
validates_format_of <span style="color: #990000">:</span>description<span style="color: #990000">,</span> <span style="color: #990000">:</span>with <span style="color: #990000">=></span> <span style="color: #FF6600">/^[a-zA-Z]+$/</span><span style="color: #990000">,</span> <span style="color: #990000">:</span>message <span style="color: #990000">=></span> <span style="color: #FF0000">"Only letters allowed"</span>
<span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
</tt></pre></div></div>
<div class="para"><p>The default error message for <tt>validates_format_of</tt> is "<em>is invalid</em>".</p></div>
<h3 id="_the_tt_validates_inclusion_of_tt_helper">3.7. The <tt>validates_inclusion_of</tt> helper</h3>
<div class="para"><p>This helper validates that the attributes' values are included in a given set. In fact, this set can be any enumerable object.</p></div>
<div class="listingblock">
<div class="content"><!-- Generator: GNU source-highlight 2.9
by Lorenzo Bettini
http://www.lorenzobettini.it
http://www.gnu.org/software/src-highlite -->
<pre><tt><span style="font-weight: bold"><span style="color: #0000FF">class</span></span> Coffee <span style="color: #990000"><</span> ActiveRecord<span style="color: #990000">::</span>Base
validates_inclusion_of <span style="color: #990000">:</span>size<span style="color: #990000">,</span> <span style="color: #990000">:</span><span style="font-weight: bold"><span style="color: #0000FF">in</span></span> <span style="color: #990000">=></span> <span style="color: #990000">%</span>w<span style="color: #990000">(</span>small medium large<span style="color: #990000">),</span> <span style="color: #990000">:</span>message <span style="color: #990000">=></span> <span style="color: #FF0000">"%s is not a valid size"</span>
<span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
</tt></pre></div></div>
<div class="para"><p>The <tt>validates_inclusion_of</tt> helper has an option <tt>:in</tt> that receives the set of values that will be accepted. The <tt>:in</tt> option has an alias called <tt>:within</tt> that you can use for the same purpose, if you'd like to. In the previous example we used the <tt>:message</tt> option to show how we can personalize it with the current attribute's value, through the <tt>%s</tt> format mask.</p></div>
<div class="para"><p>The default error message for <tt>validates_inclusion_of</tt> is "<em>is not included in the list</em>".</p></div>
<h3 id="_the_tt_validates_length_of_tt_helper">3.8. The <tt>validates_length_of</tt> helper</h3>
<div class="para"><p>This helper validates the length of your attribute's value. It can receive a variety of different options, so you can specify length contraints in different ways.</p></div>
<div class="listingblock">
<div class="content"><!-- Generator: GNU source-highlight 2.9
by Lorenzo Bettini
http://www.lorenzobettini.it
http://www.gnu.org/software/src-highlite -->
<pre><tt><span style="font-weight: bold"><span style="color: #0000FF">class</span></span> Person <span style="color: #990000"><</span> ActiveRecord<span style="color: #990000">::</span>Base
validates_length_of <span style="color: #990000">:</span>name<span style="color: #990000">,</span> <span style="color: #990000">:</span>minimum <span style="color: #990000">=></span> <span style="color: #993399">2</span>
validates_length_of <span style="color: #990000">:</span>bio<span style="color: #990000">,</span> <span style="color: #990000">:</span>maximum <span style="color: #990000">=></span> <span style="color: #993399">500</span>
validates_length_of <span style="color: #990000">:</span>password<span style="color: #990000">,</span> <span style="color: #990000">:</span><span style="font-weight: bold"><span style="color: #0000FF">in</span></span> <span style="color: #990000">=></span> <span style="color: #993399">6</span><span style="color: #990000">..</span><span style="color: #993399">20</span>
validates_length_of <span style="color: #990000">:</span>registration_number<span style="color: #990000">,</span> <span style="color: #990000">:</span>is <span style="color: #990000">=></span> <span style="color: #993399">6</span>
<span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
</tt></pre></div></div>
<div class="para"><p>The possible length constraint options are:</p></div>
<div class="ilist"><ul>
<li>
<p>
<tt>:minimum</tt> - The attribute cannot have less than the specified length.
</p>
</li>
<li>
<p>
<tt>:maximum</tt> - The attribute cannot have more than the specified length.
</p>
</li>
<li>
<p>
<tt>:in</tt> (or <tt>:within</tt>) - The attribute length must be included in a given interval. The value for this option must be a Ruby range.
</p>
</li>
<li>
<p>
<tt>:is</tt> - The attribute length must be equal to a given value.
</p>
</li>
</ul></div>
<div class="para"><p>The default error messages depend on the type of length validation being performed. You can personalize these messages, using the <tt>:wrong_length</tt>, <tt>:too_long</tt> and <tt>:too_short</tt> options and the <tt>%d</tt> format mask as a placeholder for the number corresponding to the length contraint being used. You can still use the <tt>:message</tt> option to specify an error message.</p></div>
<div class="listingblock">
<div class="content"><!-- Generator: GNU source-highlight 2.9
by Lorenzo Bettini
http://www.lorenzobettini.it
http://www.gnu.org/software/src-highlite -->
<pre><tt><span style="font-weight: bold"><span style="color: #0000FF">class</span></span> Person <span style="color: #990000"><</span> ActiveRecord<span style="color: #990000">::</span>Base
validates_length_of <span style="color: #990000">:</span>bio<span style="color: #990000">,</span> <span style="color: #990000">:</span>too_long <span style="color: #990000">=></span> <span style="color: #FF0000">"you're writing too much. %d characters is the maximum allowed."</span>
<span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
</tt></pre></div></div>
<h3 id="_the_tt_validates_numericallity_of_tt_helper">3.9. The <tt>validates_numericallity_of</tt> helper</h3>
<div class="para"><p>This helper validates that your attributes have only numeric values. By default, it will match an optional sign followed by a integral or floating point number. Using the <tt>:integer_only</tt> option set to true, you can specify that only integral numbers are allowed.</p></div>
<div class="para"><p>If you use <tt>:integer_only</tt> set to <tt>true</tt>, then it will use the <tt><span>/\A[+\-]?\d+\Z/</span></tt> regular expression to validate the attribute's value. Otherwise, it will try to convert the value using <tt>Kernel.Float</tt>.</p></div>
<div class="listingblock">
<div class="content"><!-- Generator: GNU source-highlight 2.9
by Lorenzo Bettini
http://www.lorenzobettini.it
http://www.gnu.org/software/src-highlite -->
<pre><tt><span style="font-weight: bold"><span style="color: #0000FF">class</span></span> Player <span style="color: #990000"><</span> ActiveRecord<span style="color: #990000">::</span>Base
validates_numericallity_of <span style="color: #990000">:</span>points
validates_numericallity_of <span style="color: #990000">:</span>games_played<span style="color: #990000">,</span> <span style="color: #990000">:</span>integer_only <span style="color: #990000">=></span> <span style="font-weight: bold"><span style="color: #0000FF">true</span></span>
<span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
</tt></pre></div></div>
<div class="para"><p>The default error message for <tt>validates_numericallity_of</tt> is "<em>is not a number</em>".</p></div>
<h3 id="_the_tt_validates_presence_of_tt_helper">3.10. The <tt>validates_presence_of</tt> helper</h3>
<div class="para"><p>This helper validates that the attributes are not empty. It uses the <tt>blank?</tt> method to check if the value is either <tt>nil</tt> or an empty string (if the string has only spaces, it will still be considered empty).</p></div>
<div class="listingblock">
<div class="content"><!-- Generator: GNU source-highlight 2.9
by Lorenzo Bettini
http://www.lorenzobettini.it
http://www.gnu.org/software/src-highlite -->
<pre><tt><span style="font-weight: bold"><span style="color: #0000FF">class</span></span> Person <span style="color: #990000"><</span> ActiveRecord<span style="color: #990000">::</span>Base
validates_presence_of <span style="color: #990000">:</span>name<span style="color: #990000">,</span> <span style="color: #990000">:</span>login<span style="color: #990000">,</span> <span style="color: #990000">:</span>email
<span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
</tt></pre></div></div>
<div class="admonitionblock">
<table><tr>
<td class="icon">
<img src="./images/icons/note.png" alt="Note" />
</td>
<td class="content">If you want to be sure that an association is present, you'll need to test if the foreign key used to map the association is present, and not the associated object itself.</td>
</tr></table>
</div>
<div class="listingblock">
<div class="content"><!-- Generator: GNU source-highlight 2.9
by Lorenzo Bettini
http://www.lorenzobettini.it
http://www.gnu.org/software/src-highlite -->
<pre><tt><span style="font-weight: bold"><span style="color: #0000FF">class</span></span> LineItem <span style="color: #990000"><</span> ActiveRecord<span style="color: #990000">::</span>Base
belongs_to <span style="color: #990000">:</span>order
validates_presence_of <span style="color: #990000">:</span>order_id
<span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
</tt></pre></div></div>
<div class="admonitionblock">
<table><tr>
<td class="icon">
<img src="./images/icons/note.png" alt="Note" />
</td>
<td class="content">If you want to validate the presence of a boolean field (where the real values are true and false), you will want to use validates_inclusion_of :field_name, :in ⇒ [true, false] This is due to the way Object#blank? handles boolean values. false.blank? # ⇒ true</td>
</tr></table>
</div>
<div class="para"><p>The default error message for <tt>validates_presence_of</tt> is "<em>can't be empty</em>".</p></div>
<h3 id="_the_tt_validates_size_of_tt_helper">3.11. The <tt>validates_size_of</tt> helper</h3>
<h3 id="_the_validates_uniqueness_of_helper">3.12. The validates_uniqueness_of+ helper</h3>
</div>
<h2 id="_common_validation_options">4. Common validation options</h2>
<div class="sectionbody">
</div>
<h2 id="_changelog">5. Changelog</h2>
<div class="sectionbody">
<div class="para"><p><a href="http://rails.lighthouseapp.com/projects/16213/tickets/26-active-record-validations-and-callbacks">http://rails.lighthouseapp.com/projects/16213/tickets/26-active-record-validations-and-callbacks</a></p></div>
</div>
</div>
</div>
</body>
</html>