Rails - Jul 2007 - can helpers manipulate block?

hi,

i''m unsure the best way to ask this but i''m wondering if a
rails
helper can manipulate html. for instance if i had a helper that looked
like this:

<% my_helper do %>
  <br />
<% end %>

is there a way i can programatically work with the html content (i.e.
<br />)? is there a variable available in my helper that represents
the content between the helper and end tags?

thanks in advance, mike

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Hi --

On Sat, 7 Jul 2007, Michael Bannister wrote:
> hi,
>
> i''m unsure the best way to ask this but i''m wondering if
a rails
> helper can manipulate html. for instance if i had a helper that looked
> like this:
>
> <% my_helper do %>
>  <br />
> <% end %>
>
> is there a way i can programatically work with the html content (i.e.
> <br />)? is there a variable available in my helper that represents
> the content between the helper and end tags?
Yes; you could do it like this:

   def my_helper(&block)
     string = capture(&block)
     concat(do_something_to(string), block.binding)
   end

capture grabs the content from the template; concat inserts the
manipulated string into the output stream.  You have to pass
block.binding along so that concat is operating in the right scope.


David

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Michael Bannister wrote:
> i''m unsure the best way to ask this but i''m wondering if
a rails
> helper can manipulate html. for instance if i had a helper that looked
> like this:
>
> <% my_helper do %>
>  <br />
> <% end %>
>
> is there a way i can programatically work with the html content (i.e.
> <br />)? is there a variable available in my helper that represents
> the content between the helper and end tags?
Unfortunately yes. Inside my_helper, use capture and yield. The return value 
of capture(yield), IIRC, is the HTML.

capture is sensitive to call because eRB mangles your HTML before evaluating 
it, and capture naturally sees the mangled version. Google for capture to 
see how to use it. Then use <%= my_helper, and return your version of the 
captured HTML.

And please reconsider. There''s always a way to write the correct HTML
the
first time; you shouldn''t want to search and replace inside it. For
example:

 <% my_helper do |creator| %>
   <br />
   <%= creator.create_html %>
   <br />
 <% end %>

Now my_helper initializes a creator, and this creates more HTML and inserts 
it into the block. This is generally what blocks are for - to mix and match 
objects from outside the block (like eRB) with objects inserted into the 
block by the goal-posts operator ||.

-- 
  Phlip
  http://www.oreilly.com/catalog/9780596510657/
  "Test Driven Ajax (on Rails)"
  assert_xpath, assert_javascript, & assert_ajax 


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