Ruby Instance Eval

Question

class Setter
    attr_accessor :foo

    def initialize
        @foo = "It aint easy being cheesy!"
    end

    def set
        self.instance_eval { yield if block_given? }
    end
end

options = Setter.new

# Works
options.instance_eval do
    p foo
end

# Fails
options.set do
    p foo
end

Why does the 'set' method fail?

EDIT

Figured it out...

def set
    self.instance_eval { yield if block_given? }
end

Needed to be:

def set(&blk)
    instance_eval(&blk)
end

klochner · Accepted Answer · 2009-12-16 20:27:19Z

2

Yep - yield evaluates in the context within which it was defined.

Good write up here, but a simple example shows the problem:

>> foo = "wrong foo"
>> options.set do
?>     p foo
>> end
"wrong foo"

edited Dec 16, 2009 at 20:27

answered Dec 16, 2009 at 20:21

klochner

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