Calling a block in a new scope is easy enough:
self.instance_eval &block
And calling a block, passing it parameters is easy enough:
block.call(*params)
But is there some way to do both? To both change the scope of evaluation
and pass variables into the block.
Ruby T. wrote:
Calling a block in a new scope is easy enough:
self.instance_eval &block
And calling a block, passing it parameters is easy enough:
block.call(*params)
But is there some way to do both? To both change the scope of evaluation
and pass variables into the block.
Hello,
I’m not sure I fully understand the question being asked here. Can you
provide a small bit of code to highlight what you are trying to acheive.
Do you wish to pass vaiables into the instance_eval block?
Any variables in scope when the instance_eval block is called can be
used in the instance_eval block itself. However, if you were to pass a
proc object into the instance_eval it would retain the context it was
created at.
See below for an example of this.
class Test
def initialize(arg)
@instance_variable = arg
end
end
test_obj = Test.new(“initializing_arg”)
outside = “outside instance_eval”
proc = Proc.new {|arg| puts self} #self main here
test_obj.instance_eval do
puts @instance_variable #test_obj instance variable.
puts outside #any variable from outside the block can be passed in.
puts proc #will return main rather than the object
end
Hmm, I get the feeling I have ranted about stuff that does not help you
one bit with your question…
Get back to me with a bit more detail and hopefully I’ll be able to
help!
Cheers,
Matt.
Matt G. wrote:
Ruby T. wrote:
Calling a block in a new scope is easy enough:
self.instance_eval &block
And calling a block, passing it parameters is easy enough:
block.call(*params)
But is there some way to do both? To both change the scope of evaluation
and pass variables into the block.
Hello,
I’m not sure I fully understand the question being asked here. Can you
provide a small bit of code to highlight what you are trying to acheive.
Do you wish to pass vaiables into the instance_eval block?
Any variables in scope when the instance_eval block is called can be
used in the instance_eval block itself. However, if you were to pass a
proc object into the instance_eval it would retain the context it was
created at.
See below for an example of this.
class Test
def initialize(arg)
@instance_variable = arg
end
end
test_obj = Test.new(“initializing_arg”)
outside = “outside instance_eval”
proc = Proc.new {|arg| puts self} #self main here
test_obj.instance_eval do
puts @instance_variable #test_obj instance variable.
puts outside #any variable from outside the block can be passed in.
puts proc #will return main rather than the object
end
Hmm, I get the feeling I have ranted about stuff that does not help you
one bit with your question…
Get back to me with a bit more detail and hopefully I’ll be able to
help!
Cheers,
Matt.
Oops, that last ‘puts proc’ should be proc.call(“whatever”)
If full:
class Test
def initialize(arg)
@instance_variable = arg
end
end
test_obj = Test.new(“initializing_arg”)
outside = “outside instance_eval”
proc = Proc.new {|arg| puts self} #self main here
test_obj.instance_eval do
puts @instance_variable #test_obj instance variable.
puts outside #any variable from outside the block can be passed in.
proc.call(“whatever”) #will return main rather than the object
end
On May 19, 10:07 pm, Ruby T. [email protected] wrote:
self.instance_eval &block
And calling a block, passing it parameters is easy enough:
block.call(*params)
But is there some way to do both? To both change the scope of evaluation
and pass variables into the block.
http://eigenclass.org/hiki.rb?instance_exec
On 5/20/07, Phrogz [email protected] wrote:
eigenclass.org
OP We have just discussed this twice recently, maybe you should browse
the recent posts…
Phrogz: Your link seems outdated,
c.f.eigenclass.org
for a discussion of #undef_method (bad) vs. #remove_method (good) and
please note the potential danger of endless recursion.
Cheers
Robert