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comp.lang.ruby

getting the name of arguments a method takes

didier.prophete

1/17/2006 3:25:00 AM

I am wondering if there is a way to programatically get the name of the
arguments a function take.

Say, I have this code:
class MyClass
def my_fct(a, b, c)
end
end

Now, I can easily get a handle to the method 'my_fct' using:
mc = MyClass.new
meth = mc.method(:my_fct)

But how do I get to the list of arguments of 'my_fct' ? I couldn't find
anything like:
meth.arg_list
which would return [ :a, :b, :c ], or something like that.

Is this even possible in ruby ?

-Didier

--
Posted via http://www.ruby-....
1 Answer

Timothy Goddard

1/18/2006 12:40:00 AM

0

I don't believe this is possible, but neither can I think why you would
need to. Please explain what you are trying to achieve as there may be
a better way to accomplish it. If you had a method called clean_swamp
you could obtain the number of arguments required with
method(:clean_swamp).arity but not the names. I'm not even sure these
parameter names are actually stored at all after the method has been
defined.

If you need to include usage instructions you could do something like:

$usage = Hash.new('No usage instructions defined.')

class Method
def usage
$usage[self.to_s]
end

def usage=(new_usage)
$usage[self.to_s] = new_usage
end
end

def clean_swamp(swamp, slime_amount)
swamp.slime -= slime_amount
end

method(:clean_swamp).usage = 'clean_swamp(swamp, slime_amount)'
puts method(:clean_swamp).usage