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I saw some code in a Rails v2.3 app.
In layout/car_general.html.erb (this view is called by a method in cars_controller) , I saw the code:
<body> <%= yield %> <%= javascript_include_tag 'jquery-1.4.2.min' %> <% javascript_tag do %> <%= yield :jstemplates %> var some_car = new Object; <%= yield :some_car %> <% end -%> </body> Two questions to ask:
<body>. <%= yield :jstemplates %> and what about <%= yield :some_car %> , is it point to a view or just to show the value of some_car?
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When yield is called in side a method then method requires a block with in it. A block is simply a chunk of code, and yield allows us to inject that code at some place into a method. Simple Yield: When the yield keyword used inside the body of a method, will allow us to call that method with a block of code.
It tells Rails to put your view content to this block (which is called by yield ) at that place in the layout file.
Without any arguments, yield will render the template of the current controller/action. So if you're on the cars/show page, it will render views/cars/show. html. erb .
yield tells ruby to call the block passed to the method, giving it its argument. yield will produce an error if the method wasn't called with a block where as return statement don't produces error.
Without any arguments, yield will render the template of the current controller/action. So if you're on the cars/show page, it will render views/cars/show.html.erb.
When you pass yield an argument, it lets you define content in your templates that you want to be rendered outside of that template. For example, if your cars/show page has a specific html snippet that you want to render in the footer, you could add the following to your show template and the car_general layout:
show.html.erb:
<% content_for :footer do %> This content will show up in the footer section <% end %> layouts/car_general.html.erb
<%= yield :footer %> The Rails Guide has a good section on using yield and content_for: http://guides.rubyonrails.org/layouts_and_rendering.html#understanding-yield
The API documentation for content_for is helpful too and has some other examples to follow. Note that it's for Rails 3.1.1 , but this functionality has not changed much since 2.3, if at all and should still apply for 3.0.x and 3.1.x.
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