Difference between Render and Render Partial and Yield
I have read it from the Rails guides, Have looked at Micheal Hartel book and now reading it from Rails View book but still I get confused :(
There is a _footer.html.erb file so it is a "partial" and in the code it has written:
<%=render 'layouts/footer' %>
so my understanding is that when it sees this, goes and insert the HTML for footer file in here. Ok... Now a few pages later it is saying:
<%= render partial: 'activitiy_items/recent' %>
so WHY this time we have the word "partial" in here but we didn't have it in the previous one?
And there somewhere else I see <%= yield :sidebar %>
So this yield also insert HTML in its place? Well wasn't it what render was doing?
I was hoping if another programmer instead of books explains this to me maybe I get it this time:)
Answer
render & render partial:
render 'some_view'is a shorthand forrender partial: 'some_view'.render file: 'view'will look for a fileview.html.erband NOT_view.html.erb(.erbor any other renderer you use)renderwill not accept additional local variables for the partial, you need to userender partial:as following for that:render partial: 'some/path/to/my/partial', locals: { custom_var: 'Hello' }
(http://guides.rubyonrails.org/layouts_and_rendering.html#passing-local-variables)
yield & content_for
yieldis typically used in layouts. It tells Rails to put the content for this block at that place in the layout.- When you do
yield :somethingassociated withcontent_for :something, you can pass a block of code (view) to display where theyield :somethingis placed (see example below).
A small example about yield:
In your layout:
<html>
<head>
<%= yield :html_head %>
</head>
<body>
<div id="sidebar">
<%= yield :sidebar %>
</div>
</body>
In one of your view:
<% content_for :sidebar do %>
This content will show up in the sidebar section
<% end %>
<% content_for :html_head do %>
<script type="text/javascript">
console.log("Hello World!");
</script>
<% end %>
This will produce the following HTML:
<html>
<head>
<script type="text/javascript">
console.log("Hello World!");
</script>
</head>
<body>
<div id="sidebar">
This content will show up in the sidebar section
</div>
</body>
Posts that might help:
Links to documentation & guides: