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POEarly return from a block given to instance_exec
 

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    <p>I need to allow blocks to be defined and called within the scope of a class, using <code>instance_exec</code> (via Rails 2.3.2). However, some of these blocks need to return early in some situations, which is causing me a problem.</p> <p>My application was built using ruby 1.8.6, but I need to get it running on 1.8.7 as well. It seems that between the two versions the ability to return from within a lambda was removed. The following works in 1.8.6, but throws a <code>LocalJumpError</code> (unexpected return) in 1.8.7:</p> <pre><code>class Foo def square(n) n ** 2 end def cube(n) n ** 3 end def call_block(*args, &amp;block) instance_exec *args, &amp;block end end block = lambda { |n| return square(n) if n &lt; 5 cube(n) } f = Foo.new f.call_block(5, &amp;block) # returns 125 f.call_block(3, &amp;block) # returns 9 in 1.8.6, throws a LocalJumpError in 1.8.7 </code></pre> <p>I determined that I could get it working in 1.8.7 if I replaced <code>return</code> in my block with <code>next</code>, but <code>next square(n) if n &lt; 5</code> results in <code>nil</code> in 1.8.6.</p> <p>Is there any way I can get this working in both 1.8.6 and 1.8.7? I know that I can restructure my blocks to use branching instead of an early return, but some blocks are more complex and have multiple situations where an early return is needed.</p> <p>Also, is this going to change further if I want to get my code running in ruby 1.9?</p> <p><strong>Edit:</strong> I've discovered that the reason it works in 1.8.6 and not 1.8.7 is that 1.8.7 defines its own <code>instance_exec</code> in the C source, while 1.8.6 uses Rails' implementation. If I override <code>instance_exec</code> in 1.8.7 with Rails' version, it works there too.</p>
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