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Minor rephrasing in Active Record Quering and Layouts and Rendering g…

…uides.

Example code fixes in Layouts and Rendering guide.
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1 parent d24914c commit b93c018947793e1cef4157994005dce779dae53b @kulbirsaini kulbirsaini committed Sep 24, 2010
@@ -769,13 +769,13 @@ Even though Active Record lets you specify conditions on the eager loaded associ
h3. Dynamic Finders
-For every field (also known as an attribute) you define in your table, Active Record provides a finder method. If you have a field called +first_name+ on your +Client+ model for example, you get +find_by_first_name+ and +find_all_by_first_name+ for free from Active Record. If you have also have a +locked+ field on the +Client+ model, you also get +find_by_locked+ and +find_all_by_locked+.
+For every field (also known as an attribute) you define in your table, Active Record provides a finder method. If you have a field called +first_name+ on your +Client+ model for example, you get +find_by_first_name+ and +find_all_by_first_name+ for free from Active Record. If you have a +locked+ field on the +Client+ model, you also get +find_by_locked+ and +find_all_by_locked+ methods.
-You can do +find_last_by_*+ methods too which will find the last record matching your argument.
+You can also use +find_last_by_*+ methods which will find the last record matching your argument.
You can specify an exclamation point (<tt>!</tt>) on the end of the dynamic finders to get them to raise an +ActiveRecord::RecordNotFound+ error if they do not return any records, like +Client.find_by_name!("Ryan")+
-If you want to find both by name and locked, you can chain these finders together by simply typing +and+ between the fields for example +Client.find_by_first_name_and_locked("Ryan", true)+.
+If you want to find both by name and locked, you can chain these finders together by simply typing +and+ between the fields. For example, +Client.find_by_first_name_and_locked("Ryan", true)+.
There's another set of dynamic finders that let you find or create/initialize objects if they aren't found. These work in a similar fashion to the other finders and can be used like +find_or_create_by_first_name(params[:first_name])+. Using this will first perform a find and then create if the find returns +nil+. The SQL looks like this for +Client.find_or_create_by_first_name("Ryan")+:
@@ -27,7 +27,7 @@ I'll cover each of these methods in turn. But first, a few words about the very
h4. Rendering by Default: Convention Over Configuration in Action
-You've heard that Rails promotes "convention over configuration." Default rendering is an excellent example of this. By default, controllers in Rails automatically render views with names that correspond to valid routes. For example, if you have this code in your +BooksController+ class:
+You've heard that Rails promotes "convention over configuration". Default rendering is an excellent example of this. By default, controllers in Rails automatically render views with names that correspond to valid routes. For example, if you have this code in your +BooksController+ class:
<ruby>
class BooksController < ApplicationController
@@ -46,7 +46,7 @@ And you have a view file +app/views/books/index.html.erb+:
<h1>Books are coming soon!</h1>
</ruby>
-Rails will automatically render +app/views/books/index.html.erb+ when you navigate to +/books+ and you will see on your screen that "Books are coming soon!"
+Rails will automatically render +app/views/books/index.html.erb+ when you navigate to +/books+ and you will see "Books are coming soon!" on your screen.
However a coming soon screen is only minimally useful, so you will soon create your +Book+ model and add the index action to +BooksController+:
@@ -58,9 +58,9 @@ class BooksController < ApplicationController
end
</ruby>
-Note that again, we have convention over configuration, in that there is no explicit render at the end of this index action. The rule is that if you do not explicitly render something by the end of the controller action, rails will look for the +action_name.html.erb+ template in the controllers view path and then render that, so in this case, Rails will render the +app/views/books/index.html.erb+ file.
+Note that we don't have explicit render at the end of the index action in accordance with "convention over configuration" principle. The rule is that if you do not explicitly render something at the end of a controller action, Rails will automatically look for the +action_name.html.erb+ template in the controller's view path and render it. So in this case, Rails will render the +app/views/books/index.html.erb+ file.
-So in our view, we want to display the properties of all the books, we could do this with an ERB template like this:
+If we want to display the properties of all the books in our view, we can do so with an ERB template like this:
<ruby>
<h1>Listing Books</h1>
@@ -123,7 +123,7 @@ Cache-Control: no-cache
$
</shell>
-We see there is an empty response (no data after the +Cache-Control+ line), but that Rails has set the response to 200 OK, so the request was successful. You can set the +:status+ options on render to change this response. Rendering nothing can be useful for AJAX requests where all you want to send back to the browser is an acknowledgement that the request was completed.
+We see there is an empty response (no data after the +Cache-Control+ line), but the request was successful because Rails has set the response to 200 OK. You can set the +:status+ options on render to change this response. Rendering nothing can be useful for AJAX requests where all you want to send back to the browser is an acknowledgement that the request was completed.
TIP: You should probably be using the +head+ method, discussed later in this guide, instead of +render :nothing+. This provides additional flexibility and makes it explicit that you're only generating HTTP headers.
@@ -134,11 +134,10 @@ If you want to render the view that corresponds to a different action within the
<ruby>
def update
@book = Book.find(params[:id])
- if @book.update_attributes(params[:book])
- redirect_to(@book)
- else
- render "edit"
- end
+ if @book.update_attributes(params[:book])
+ redirect_to(@book)
+ else
+ render "edit"
end
end
</ruby>
@@ -150,11 +149,10 @@ If you prefer, you can use a symbol instead of a string to specify the action to
<ruby>
def update
@book = Book.find(params[:id])
- if @book.update_attributes(params[:book])
- redirect_to(@book)
- else
- render :edit
- end
+ if @book.update_attributes(params[:book])
+ redirect_to(@book)
+ else
+ render :edit
end
end
</ruby>
@@ -164,11 +162,10 @@ To be explicit, you can use +render+ with the +:action+ option (though this is n
<ruby>
def update
@book = Book.find(params[:id])
- if @book.update_attributes(params[:book])
- redirect_to(@book)
- else
- render :action => "edit"
- end
+ if @book.update_attributes(params[:book])
+ redirect_to(@book)
+ else
+ render :action => "edit"
end
end
</ruby>
@@ -208,13 +205,13 @@ The +:file+ option takes an absolute file-system path. Of course, you need to ha
NOTE: By default, the file is rendered without using the current layout. If you want Rails to put the file into the current layout, you need to add the +:layout => true+ option.
-TIP: If you're running on Microsoft Windows, you should use the +:file+ option to render a file, because Windows filenames do not have the same format as Unix filenames.
+TIP: If you're running Rails on Microsoft Windows, you should use the +:file+ option to render a file, because Windows filenames do not have the same format as Unix filenames.
h5. Wrapping it up
-The above three methods of render (rendering another template within the controller, rendering a template within another controller and rendering an arbitrary file on the file system) are actually all variants of the same action.
+The above three ways of rendering (rendering another template within the controller, rendering a template within another controller and rendering an arbitrary file on the file system) are actually variants of the same action.
-In fact, in the BooksController method, inside of the edit action where we want to render the edit template if the book does not update successfully, all of the following render calls would all render the +edit.html.erb+ template in the +views/books+ directory:
+In fact, in the BooksController class, inside of the edit action where we want to render the edit template if the book does not update successfully, all of the following render calls would all render the +edit.html.erb+ template in the +views/books+ directory:
<ruby>
render :edit
@@ -241,12 +238,12 @@ The +render+ method can do without a view completely, if you're willing to use t
<ruby>
render :inline =>
- "<% products.each do |p| %><p><%= p.name %><p><% end %>"
+ "<% products.each do |p| %><p><%= p.name %></p><% end %>"
</ruby>
WARNING: There is seldom any good reason to use this option. Mixing ERB into your controllers defeats the MVC orientation of Rails and will make it harder for other developers to follow the logic of your project. Use a separate erb view instead.
-By default, inline rendering uses ERb. You can force it to use Builder instead with the +:type+ option:
+By default, inline rendering uses ERB. You can force it to use Builder instead with the +:type+ option:
<ruby>
render :inline =>
@@ -275,7 +272,7 @@ render :text => "OK"
TIP: Rendering pure text is most useful when you're responding to AJAX or web service requests that are expecting something other than proper HTML.
-NOTE: By default, if you use the +:text+ option the text is rendered without using the current layout. If you want Rails to put the text into the current layout, you need to add the +:layout => true+ option.
+NOTE: By default, if you use the +:text+ option, the text is rendered without using the current layout. If you want Rails to put the text into the current layout, you need to add the +:layout => true+ option.
h5. Rendering JSON
@@ -498,7 +495,7 @@ def show
end
</ruby>
-If +@book.special?+ evaluates to +true+, Rails will start the rendering process to dump the +@book+ variable into the +special_show+ view. But this will _not_ stop the rest of the code in the +show+ action from running, and when Rails hits the end of the action, it will start to render the +show+ view - and throw an error. The solution is simple: make sure that you only have one call to +render+ or +redirect+ in a single code path. One thing that can help is +and return+. Here's a patched version of the method:
+If +@book.special?+ evaluates to +true+, Rails will start the rendering process to dump the +@book+ variable into the +special_show+ view. But this will _not_ stop the rest of the code in the +show+ action from running, and when Rails hits the end of the action, it will start to render the +regular_show+ view - and throw an error. The solution is simple: make sure that you have only one call to +render+ or +redirect+ in a single code path. One thing that can help is +and return+. Here's a patched version of the method:
<ruby>
def show
@@ -568,7 +565,7 @@ def show
end
</ruby>
-With the code in this form, there will be likely be a problem if the +@book+ variable is +nil+. Remember, a +render :action+ doesn't run any code in the target action, so nothing will set up the +@books+ variable that the +index+ view is presumably depending on. One way to fix this is to redirect instead of rendering:
+With the code in this form, there will likely be a problem if the +@book+ variable is +nil+. Remember, a +render :action+ doesn't run any code in the target action, so nothing will set up the +@books+ variable that the +index+ view is presumably depending on. One way to fix this is to redirect instead of rendering:
<ruby>
def index
@@ -585,7 +582,7 @@ end
With this code, the browser will make a fresh request for the index page, the code in the +index+ method will run, and all will be well.
-The only downside to this code, is that it requires a round trip to the browser, the browser requested the show action with +/books/1+ and the controller finds that there are no books, so the controller sends out a 301 redirect response to the browser telling it to go to +/books/+, the browser complies and sends a new request back to the controller asking now for the +index+ action, the controller then gets all the books in the database and renders the index template, sending it back down to the browser which then shows it on your screen.
+The only downside to this code, is that it requires a round trip to the browser, the browser requested the show action with +/books/1+ and the controller finds that there are no books, so the controller sends out a 302 redirect response to the browser telling it to go to +/books/+, the browser complies and sends a new request back to the controller asking now for the +index+ action, the controller then gets all the books in the database and renders the index template, sending it back down to the browser which then shows it on your screen.
While in a small app, this added latency might not be a problem, it is something to think about when speed of response is of the essence. One way to handle this double request (though a contrived example) could be:
@@ -603,7 +600,7 @@ def show
end
</ruby>
-Which would detect that there are no books populate the +@books+ instance variable with all the books in the database and then directly render the +index.html.erb+ template returning it to the browser with a flash alert message telling the user what happened.
+Which would detect that there are no books, populate the +@books+ instance variable with all the books in the database and then directly render the +index.html.erb+ template returning it to the browser with a flash alert message telling the user what happened.
h4. Using +head+ To Build Header-Only Responses
@@ -806,7 +803,9 @@ You can even use dynamic paths such as +cache/#{current_site}/main/display+.
h5. Linking to Images with +image_tag+
-The +image_tag+ helper builds an HTML +&lt;img /&gt;+ tag to the specified file. By default, files are loaded from +public/images+, note, you must specify the extension, previous versions of Rails would allow you to just call the image name and would append +.png+ if no extension was given, Rails 3.0 does not.
+The +image_tag+ helper builds an HTML +&lt;img /&gt;+ tag to the specified file. By default, files are loaded from +public/images+.
+
+WARNING: Note that you must specify the extension of the image. Previous versions of Rails would allow you to just use the image name and would append +.png+ if no extension was given but Rails 3.0 does not.
<erb>
<%= image_tag "header.png" %>
@@ -843,7 +842,7 @@ You can also specify a special size tag, in the format "{width}x{height}":
<%= image_tag "home.gif", :size => "50x20" %>
</erb>
-In addition to the above special tags, you can supply a final hash of standard HTML options, such as +:class+ or +:id+ or +:name+:
+In addition to the above special tags, you can supply a final hash of standard HTML options, such as +:class+, +:id+ or +:name+:
<erb>
<%= image_tag "home.gif", :alt => "Go Home",
@@ -1087,7 +1086,7 @@ Partials are very useful in rendering collections. When you pass a collection to
When a partial is called with a pluralized collection, then the individual instances of the partial have access to the member of the collection being rendered via a variable named after the partial. In this case, the partial is +_product+, and within the +_product+ partial, you can refer to +product+ to get the instance that is being rendered.
-In Rails 3.0 there is also a shorthand for this, assuming +@products+ is a collection of +product+ instances, you can simply do in the +index.html.erb+:
+In Rails 3.0, there is also a shorthand for this. Assuming +@products+ is a collection of +product+ instances, you can simply write this in the +index.html.erb+:
<erb>
<h1>Products</h1>

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