Block that takes a block

[Edward Faulkner]

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How can I make a block that takes a block argument? This doesn't parse:

myproc =3D proc{|&blk| [1,2,3].each(&blk)}

The main reason I want to do this is to create a method with
'define_method' that takes a block argument. =20

For example, the 'before' method below works fine, until you apply it
to a method that takes a block. =20

class Object
# Is there a built-in way to do this?
def metaclass; class << self; self; end; end

# Call blk before each invocation of method_name
def before(method_name, &blk)
oldblk =3D method(method_name)
metaclass.instance_eval {
define_method(method_name){|*args|
blk.call(*args)
oldblk.call(*args)
}
}
end
end

thanks,
Ed

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[Brian Mitchell]

How can I make a block that takes a block argument? This doesn't parse:

myproc =3D proc{|&blk| [1,2,3].each(&blk)}

The main reason I want to do this is to create a method with
'define_method' that takes a block argument.

For example, the 'before' method below works fine, until you apply it
to a method that takes a block.

class Object
# Is there a built-in way to do this?
def metaclass; class << self; self; end; end

# Call blk before each invocation of method_name
def before(method_name, &blk)
oldblk =3D method(method_name)
metaclass.instance_eval {
define_method(method_name){|*args|
blk.call(*args)
oldblk.call(*args)
}
}
end
end

thanks,
Ed


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I believe this is a limitation in the current 1.8 series. This has
been lifted in HEAD.

You might want to consider using a smart intermediate method that is a
wrapper around the block which can safely take an instance of Proc.

Brian.