Getting method parameters in specified order

[Chintana Wilamuna]

Hi,

If I declare a function that expects 3 arguments,

def bar(x, y, z)
...
end

and later, if I have the function name in a string, is there a way to
get the parameter names using reflection in Ruby? Something similar
to the following PHP snippet,

$a = new ReflectionFunction("function_name");
$a->getParameters();

Thanks in advance,

Bye,

-Chintana

 

[Bernardo Monteiro Rufino]

[Note: parts of this message were removed to make it a legal post.]

I think we cant do more than this:

irb(main):001:0> def test(a, b, c)
irb(main):002:1> end
=> nil
irb(main):003:0> methodtest).arity
=> 3

 

[Chintana Wilamuna]

I think we cant do more than this:

irb(main):001:0> def test(a, b, c)
irb(main):002:1> end
=> nil
irb(main):003:0> methodtest).arity
=> 3

Thanks Bernardo.

Bye,

-Chintana

 

[Phrogz]

Hi,

If I declare a function that expects 3 arguments,

def bar(x, y, z)
...
end

and later, if I have the function name in a string, is there a way to
get the parameter names using reflection in Ruby?

There is not; as Bernardo said, Ruby only allows you to check the
arity of the method.

I had a need for this, too. (I was working on a project that allowed
developers to provide arbitrary Ruby-based plugins, and the GUI of the
application needed to expose the methods and their paramters
visually.)

For that need, I wrote this:
http://phrogz.net/RubyLibs/rdoc/classes/DescribeMethods.html

 

[Peña, Botp]

From: Chintana Wilamuna [mailto:[email protected]]=20
# Sent: Thursday, December 13, 2007 11:40 PM
# To: ruby-talk ML
# Subject: Re: Getting method parameters in specified order
#=20
# On Dec 13, 2007 6:36 PM, Bernardo Monteiro Rufino=20
#=20
# > I think we cant do more than this:
# >
# > irb(main):001:0> def test(a, b, c)
# > irb(main):002:1> end
# > =3D> nil
# > irb(main):003:0> methodtest).arity
# > =3D> 3

not part of ruby itself, but try looking at ruby2ruby

kind regards -botp

 

[Chintana Wilamuna]

[snip]

Thanks Botp and Phrogz, I'll look into it.

Bye,

-Chintana

--=20
http://engwar.com/

 

[Lloyd Linklater]

Hi,

If I declare a function that expects 3 arguments,

def bar(x, y, z)
...
end

and later, if I have the function name in a string, is there a way to
get the parameter names using reflection in Ruby? Something similar
to the following PHP snippet,

$a = new ReflectionFunction("function_name");
$a->getParameters();

Forgive the naive thoughts of a ruby ruby, but what if you accepted an
array as the parameter? You could use any number of elements and you
would always know which is which.

 

[Lloyd Linklater]

Forgive the naive thoughts of a ruby ruby...

ruby nuby, I meant. heh

 

[Ezra Zygmuntowicz]

Hi~

Forgive the naive thoughts of a ruby ruby, but what if you accepted an
array as the parameter? You could use any number of elements and you
would always know which is which.

You can accomplish this with the Ruby2Ruby gem. Here is a pastie of
some code that can do this for you:

http://pastie.caboo.se/128959

Here is how you can use it:

~/_merb/merb > irb -r get_args.rb

class Foo
def hi(a,b,c)
p a,b,c
end
end => nil
Foo.instance_methodhi).get_args => [[:a], [:b], [:c]]

Cheers-

- Ezra Zygmuntowicz
-- Founder & Software Architect
-- (e-mail address removed)
-- EngineYard.com