A better way to conditionally display info in views?

I find myse开发者_Go百科lf frequently writing code like this in the HTML HEAD and other places:

<% if @canonical_url %>
  <link rel="canonical" href="<%= @canonical_url %>"/>
<% end %>

I then set the variable in the controller if it's appropriate.

Is there any way of writing the equivalent on one line, or maybe a different way of organizing the code?

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Sorry for the double answer, SO will only let me post one URL.

Alternatively, your problem might be solved by using content_for in your views where you want to have this content appear in your layout.

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Ok, I came up with this solution. In the template:

<%= show_if('<link rel="canonical" href="$1"/>', @canonical_url) %>

And then the helper method:

#
# Return the template text if the variable has a value.
#
def show_if(template, variable)
  if variable
    template.gsub('$1', variable)
  else
    ''
  end
end

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I'd need a bit more context to determine what it is that you're trying to do. Given the information that you provide, I would recommend taking a look at the canonical-url plugin for Rails.

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def if_value(value, &block)
  if value
    concat(capture(value, &block))
  end
end

<% if_value(@canonical_url) do |value| %>
  <link rel="canonical" href="<%= value %>"/>
<% end %>