/
chap-demoapp.lyx
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chap-demoapp.lyx
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#LyX 1.6.1 created this file. For more info see http://www.lyx.org/
\lyxformat 345
\begin_document
\begin_header
\textclass book
\use_default_options false
\language english
\inputencoding auto
\font_roman default
\font_sans default
\font_typewriter default
\font_default_family default
\font_sc false
\font_osf false
\font_sf_scale 100
\font_tt_scale 100
\graphics default
\paperfontsize default
\spacing single
\use_hyperref false
\papersize default
\use_geometry false
\use_amsmath 1
\use_esint 1
\cite_engine basic
\use_bibtopic false
\paperorientation portrait
\secnumdepth 3
\tocdepth 3
\paragraph_separation indent
\defskip medskip
\quotes_language english
\papercolumns 1
\papersides 1
\paperpagestyle default
\tracking_changes false
\output_changes false
\author ""
\author ""
\end_header
\begin_body
\begin_layout Chapter
PocketChange
\end_layout
\begin_layout Standard
As a way to demonstrate the concepts in the book, we've decided to build
an as an evolutionary example.
The application we've picked is an Expense Tracker and we're calling it
\shape italic
PocketChange.
\end_layout
\begin_layout Standard
\begin_inset Float figure
placement h
wide false
sideways false
status open
\begin_layout Plain Layout
\align center
\begin_inset Graphics
filename images/pocketchange.png
width 6in
\end_inset
\end_layout
\begin_layout Plain Layout
\begin_inset Caption
\begin_layout Plain Layout
The PocketChange App
\end_layout
\end_inset
\end_layout
\end_inset
\end_layout
\begin_layout Standard
PocketChange will track your expenses, keep a running total of what you've
spent, allow you to organize by tags, and visualize the data.
During the later chapters of the book we'll add a few fun features such
as AJAX charting and allowing multiple people per account (with Comet update
of entries).
Above all, we want to keep the interface lean, mean and clean.
\end_layout
\begin_layout Standard
We're going to be using the
\emph on
View First
\emph default
pattern for the design of our app, since Lift's separation of presentation
and logic via templating, views, and snippets lends itself to
\emph on
View First
\emph default
so well.
For an excellent article on the design decisions behind Lift's approach
to templating and logic, read David Pollak's
\emph on
Lift View First
\emph default
article on the wiki
\begin_inset Foot
status open
\begin_layout Plain Layout
\begin_inset Flex URL
status collapsed
\begin_layout Plain Layout
http://wiki.liftweb.net/index.php?title=Lift_View_First
\end_layout
\end_inset
.
Note that the example code is somewhat out of date on this page; the interestin
g part is David's reasoning and decisions that have made Lift so easy to
use.
\end_layout
\end_inset
.
\end_layout
\begin_layout Standard
Another important thing to note is that we're going to breeze through the
app and touch on a lot of details.
We'll provide plenty of references to the chapters where things are covered;
this chapter is really intended to just give you a taste of Lift, so feel
free to read ahead if you want more info on how something works.
Full source for the entire PocketChange application is available at GitHub
\begin_inset Foot
status open
\begin_layout Plain Layout
\begin_inset CommandInset href
LatexCommand href
target "http://github.com/tjweir/pocketchangeapp/tree"
\end_inset
\end_layout
\end_inset
.
Enough chatter, let's go!
\end_layout
\begin_layout Section
Defining the Model
\end_layout
\begin_layout Standard
The first step we'll take is to define the database entities that we're
going to use for our app.
The base functionality of a categorized expense tracker is covered by the
following items:
\end_layout
\begin_layout Itemize
User - representing a user of the application
\end_layout
\begin_layout Itemize
Account - representing a specific expense account.
We want to support more than one per user
\end_layout
\begin_layout Itemize
Expense - representing a specific expense transaction tied to a particular
account
\end_layout
\begin_layout Itemize
Tag - Allows us a to categorize each expense for later searching and reporting
\end_layout
\begin_layout Standard
We'll start out with the User, as shown in listing
\begin_inset CommandInset ref
LatexCommand ref
reference "lst:PocketChange-User-entity"
\end_inset
.
We leverage Lift's MegaProtoUser (section
\begin_inset CommandInset ref
LatexCommand vref
reference "sub:ProtoUser-and-MegaProtoUser"
\end_inset
) class to handle 99% of everything we need for user management.
For example, with just the code you see, we define an entire user management
function for our site, including signup page, lost password page, and login
page.
The accompanying SiteMap (section
\begin_inset CommandInset ref
LatexCommand vref
reference "cha:SiteMap"
\end_inset
) menus are generated with a single call to
\family typewriter
User.siteMap
\family default
.
As you can see, we can customize the XHTML that's generated for the user
management pages with a few simple defs; the customization for MetaMegaProtoUse
r is extensive.
\end_layout
\begin_layout Standard
\begin_inset listings
inline false
status open
\begin_layout Plain Layout
\begin_inset Caption
\begin_layout Plain Layout
PocketChange User entity
\begin_inset CommandInset label
LatexCommand label
name "lst:PocketChange-User-entity"
\end_inset
\end_layout
\end_inset
\end_layout
\begin_layout Plain Layout
package com.pocketchangeapp.model
\end_layout
\begin_layout Plain Layout
\end_layout
\begin_layout Plain Layout
import _root_.net.liftweb.mapper._
\end_layout
\begin_layout Plain Layout
\end_layout
\begin_layout Plain Layout
object User extends User with MetaMegaProtoUser[User] {
\end_layout
\begin_layout Plain Layout
override def dbTableName = "users" // define the DB table name
\end_layout
\begin_layout Plain Layout
// Spruce up the forms a bit
\end_layout
\begin_layout Plain Layout
override def loginXhtml =
\end_layout
\begin_layout Plain Layout
<lift:surround with="default" at="content">
\end_layout
\begin_layout Plain Layout
{ super.loginXhtml }
\end_layout
\begin_layout Plain Layout
</lift:surround>
\end_layout
\begin_layout Plain Layout
\end_layout
\begin_layout Plain Layout
override def signupXhtml(user: User) =
\end_layout
\begin_layout Plain Layout
<lift:surround with="default" at="content">
\end_layout
\begin_layout Plain Layout
{ super.signupXhtml(user) }
\end_layout
\begin_layout Plain Layout
</lift:surround>
\end_layout
\begin_layout Plain Layout
}
\end_layout
\begin_layout Plain Layout
\end_layout
\begin_layout Plain Layout
class User extends MegaProtoUser[User] {
\end_layout
\begin_layout Plain Layout
def getSingleton = User // what's the "meta" server
\end_layout
\begin_layout Plain Layout
def allAccounts : List[Account] =
\end_layout
\begin_layout Plain Layout
Account.findAll(By(Account.owner, this.id))
\end_layout
\begin_layout Plain Layout
}
\end_layout
\end_inset
\end_layout
\begin_layout Standard
Note that we've also added a utility method to the User class to retrieve
all of the accounts for a given user.
We use the MetaMapper.findAll method to do a query by owner id (section
\begin_inset CommandInset ref
LatexCommand vref
reference "sub:Querying-for-Entities"
\end_inset
).
\end_layout
\begin_layout Standard
Defining the Account entity is a little more involved, as shown in listing
\begin_inset CommandInset ref
LatexCommand ref
reference "lst:PocketChange-Account-entity"
\end_inset
.
Here we define a class with a Long primary key and some fields associate
with the accounts.
We also define some helper methods for object relationship joins (section
\begin_inset CommandInset ref
LatexCommand vref
reference "sub:helper-joins"
\end_inset
).
The Expense and Tag entities (along with some ancillary entities) follow
suit, so we won't cover them here.
\end_layout
\begin_layout Standard
\begin_inset listings
inline false
status open
\begin_layout Plain Layout
\begin_inset Caption
\begin_layout Plain Layout
PocketChange Account entity
\begin_inset CommandInset label
LatexCommand label
name "lst:PocketChange-Account-entity"
\end_inset
\end_layout
\end_inset
\end_layout
\begin_layout Plain Layout
package com.pocketchangeapp.model
\end_layout
\begin_layout Plain Layout
\end_layout
\begin_layout Plain Layout
import java.math.MathContext
\end_layout
\begin_layout Plain Layout
import net.liftweb.mapper._
\end_layout
\begin_layout Plain Layout
import net.liftweb.util.Empty
\end_layout
\begin_layout Plain Layout
\end_layout
\begin_layout Plain Layout
class Account extends LongKeyedMapper[Account] with IdPK {
\end_layout
\begin_layout Plain Layout
def getSingleton = Account
\end_layout
\begin_layout Plain Layout
object owner extends MappedLongForeignKey(this, User) {
\end_layout
\begin_layout Plain Layout
override def dbIndexed_? = true
\end_layout
\begin_layout Plain Layout
}
\end_layout
\begin_layout Plain Layout
def admins = AccountAdmin.findAll(By(AccountAdmin.account, this.id))
\end_layout
\begin_layout Plain Layout
def addAdmin (user : User) =
\end_layout
\begin_layout Plain Layout
AccountAdmin.create.account(this).administrator(user).save
\end_layout
\begin_layout Plain Layout
def viewers = AccountViewer.findAll(By(AccountViewer.account, this.id))
\end_layout
\begin_layout Plain Layout
object is_public extends MappedBoolean(this) {
\end_layout
\begin_layout Plain Layout
override def defaultValue = false
\end_layout
\begin_layout Plain Layout
}
\end_layout
\begin_layout Plain Layout
// The balance has up to 16 digits and 2 decimal places
\end_layout
\begin_layout Plain Layout
object balance extends MappedDecimal(this, MathContext.DECIMAL64, 2)
\end_layout
\begin_layout Plain Layout
def entries = Expense.getByAcct(this, Empty, Empty, Empty)
\end_layout
\begin_layout Plain Layout
def tags = Tag.findAll(By(Tag.account, this.id))
\end_layout
\begin_layout Plain Layout
object name extends MappedString(this,100)
\end_layout
\begin_layout Plain Layout
object description extends MappedString(this, 300)
\end_layout
\begin_layout Plain Layout
object externalAccount extends MappedString(this, 300)
\end_layout
\begin_layout Plain Layout
def notes = AccountNote.findAll(By(AccountNote.account, this.id))
\end_layout
\begin_layout Plain Layout
}
\end_layout
\begin_layout Plain Layout
\end_layout
\begin_layout Plain Layout
object Account extends Account with LongKeyedMetaMapper[Account] {
\end_layout
\begin_layout Plain Layout
def findByName (owner : User, name : String) : List[Account] =
\end_layout
\begin_layout Plain Layout
Account.findAll(By(Account.owner, owner.id.is), By(Account.name, name))
\end_layout
\begin_layout Plain Layout
}
\end_layout
\end_inset
\end_layout
\begin_layout Section
Our First Template
\end_layout
\begin_layout Standard
Our next step is to figure out how we'll present this data to the user.
We'd like to show a home page on the site that shows either a welcome message
or a summary of account balances and a place to enter new expenses depending
on whether the user is logged in.
Listing
\begin_inset CommandInset ref
LatexCommand ref
reference "lst:The-welcome-template"
\end_inset
shows a basic template to handle this that we'll save in index.html.
The astute reader will notice that we have a head element but no body.
This is XHTML, so how does this work? This template uses the
\family typewriter
<lift:surround>
\family default
tag (section
\begin_inset CommandInset ref
LatexCommand vref
reference "sub:surround-tag"
\end_inset
) to embed itself into a master template (
\family typewriter
/templates_hidden/default
\family default
); Lift actually does what's called a
\begin_inset Quotes eld
\end_inset
head merge
\begin_inset Quotes erd
\end_inset
(section
\begin_inset CommandInset ref
LatexCommand vref
reference "sec:Head-Merge"
\end_inset
) to include the contents of the
\family typewriter
head
\family default
tag in our template within the
\family typewriter
head
\family default
element of the master template.
The
\family typewriter
<lift:HomePage.summary>
\family default
and
\family typewriter
<lift:AddEntry.addentry>
\family default
tags are snippet definitions.
Snippets are the backing Scala code the control the actual page logic;
we'll be covering them in the next section.
\end_layout
\begin_layout Standard
\begin_inset listings
lstparams "language=XML"
inline false
status open
\begin_layout Plain Layout
\begin_inset Caption
\begin_layout Plain Layout
The welcome template
\begin_inset CommandInset label
LatexCommand label
name "lst:The-welcome-template"
\end_inset
\end_layout
\end_inset
\end_layout
\begin_layout Plain Layout
<lift:surround with="default" at="content">
\end_layout
\begin_layout Plain Layout
<head>
\end_layout
\begin_layout Plain Layout
<!-- required plugins -->
\end_layout
\begin_layout Plain Layout
<script type="text/javascript" src="/scripts/date.js"></script>
\end_layout
\begin_layout Plain Layout
<!--[if IE]>
\end_layout
\begin_layout Plain Layout
<script type="text/javascript" src="/scripts/jquery.bgiframe.js">
\end_layout
\begin_layout Plain Layout
</script>
\end_layout
\begin_layout Plain Layout
<![endif]-->
\end_layout
\begin_layout Plain Layout
\end_layout
\begin_layout Plain Layout
<!-- jquery.datePicker.js -->
\end_layout
\begin_layout Plain Layout
<script type="text/javascript" src="/scripts/jquery.datePicker.js">
\end_layout
\begin_layout Plain Layout
</script>
\end_layout
\begin_layout Plain Layout
<link rel="stylesheet" type="text/css" href="/style/datePicker.css" />
\end_layout
\begin_layout Plain Layout
</head>
\end_layout
\begin_layout Plain Layout
<lift:HomePage.summary>
\end_layout
\begin_layout Plain Layout
<div class="column span-24 bordered">
\end_layout
\begin_layout Plain Layout
<h2>Summary of accounts:</h2>
\end_layout
\begin_layout Plain Layout
<account:entry>
\end_layout
\begin_layout Plain Layout
<acct:name /> : <acct:balance /> <br/>
\end_layout
\begin_layout Plain Layout
</account:entry>
\end_layout
\begin_layout Plain Layout
</div>
\end_layout
\begin_layout Plain Layout
<hr />
\end_layout
\begin_layout Plain Layout
</lift:HomePage.summary>
\end_layout
\begin_layout Plain Layout
\end_layout
\begin_layout Plain Layout
<div class="column span-24">
\end_layout
\begin_layout Plain Layout
<lift:AddEntry.addentry form="POST">
\end_layout
\begin_layout Plain Layout
<div id="entryform">
\end_layout
\begin_layout Plain Layout
<div class="column span-24"><h3>Entry Form</h3>
\end_layout
\begin_layout Plain Layout
<e:account /> <e:dateOf /> <e:desc /> <e:value />
\end_layout
\begin_layout Plain Layout
<e:tags/><button>Add $</button>
\end_layout
\begin_layout Plain Layout
</div>
\end_layout
\begin_layout Plain Layout
</div>
\end_layout
\begin_layout Plain Layout
</lift:AddEntry.addentry>
\end_layout
\begin_layout Plain Layout
</div>
\end_layout
\begin_layout Plain Layout
\end_layout
\begin_layout Plain Layout
<script type="text/javascript">
\end_layout
\begin_layout Plain Layout
Date.format = 'yyyy/mm/dd';
\end_layout
\begin_layout Plain Layout
jQuery(function () {
\end_layout
\begin_layout Plain Layout
jQuery('#entrydate').datePicker({startDate:'00010101',
\end_layout
\begin_layout Plain Layout
clickInput:true});
\end_layout
\begin_layout Plain Layout
})
\end_layout
\begin_layout Plain Layout
</script>
\end_layout
\begin_layout Plain Layout
</lift:surround>
\end_layout
\end_inset
\end_layout
\begin_layout Standard
As you can see, there's no control logic at all in our template, just well-forme
d XML and some javascript to activate the jQuery datePicker functionality.
\end_layout
\begin_layout Section
Writing Snippets
\end_layout
\begin_layout Standard
Now that we have a template, we need to write the summary and addEntry snippets
so that we can actually do something with the site.
First, let's look at the summary snippet, shown in listing
\begin_inset CommandInset ref
LatexCommand ref
reference "lst:Defining-the-summary-snippet"
\end_inset
.
We've skipped the standard Lift imports (listing
\begin_inset CommandInset ref
LatexCommand ref
reference "lst:Standard-import-statements"
\end_inset
) to save space, but we've specifically imported
\family typewriter
java.util.Date
\family default
and all of our Model classes.
\end_layout
\begin_layout Standard
\begin_inset listings
inline false
status open
\begin_layout Plain Layout
\begin_inset Caption
\begin_layout Plain Layout
Defining the summary snippet
\begin_inset CommandInset label
LatexCommand label
name "lst:Defining-the-summary-snippet"
\end_inset
\end_layout
\end_inset
\end_layout
\begin_layout Plain Layout
package com.pocketchangeapp.snippet
\end_layout
\begin_layout Plain Layout
\end_layout
\begin_layout Plain Layout
import ...
standard imports ...
\end_layout
\begin_layout Plain Layout
import com.pocketchangeapp.model._
\end_layout
\begin_layout Plain Layout
import java.util.Date
\end_layout
\begin_layout Plain Layout