Parameter names from reflection?


#1

Is there a way to use reflection or some other method to return the
names of
the parameters a method uses? I know that ‘arity’ will return the
number of
parameters, but I’m looking for the names of them.

Thanks in advance,
Charlie


#2

On 11/14/05, Charlie S. removed_email_address@domain.invalid wrote:

Is there a way to use reflection or some other method to return the names of
the parameters a method uses?

No. Why do you need this?

Ryan


#3

On Nov 14, 2005, at 1:48 PM, Ryan L. wrote:

On 11/14/05, Charlie S. removed_email_address@domain.invalid wrote:

Is there a way to use reflection or some other method to return
the names of
the parameters a method uses?

No. Why do you need this?

Actually, ParseTree can give you this information.

http://rubyforge.org/projects/parsetree


#4

If you can get the binding from the start of the method you can look at
#local_variables.

T.


#5

Thanks for the feedback. I need a way to do this without changing the
method
itself. I’m trying to get an external program a list of parameters from
a
Ruby source file. I suppose I could write a parse script.

“Robert K.” removed_email_address@domain.invalid wrote in message
news:removed_email_address@domain.invalid…


#6

Trans wrote:

If you can get the binding from the start of the method you can look
at #local_variables.

IMHO you can’t do that without changing the method. Charlie asked for a
solution using reflection so I think this is not an option for him.

Kind regards

robert

#7

On 11/16/05, Charlie S. removed_email_address@domain.invalid wrote:

Thanks for the feedback. I need a way to do this without changing the method
itself. I’m trying to get an external program a list of parameters from a
Ruby source file. I suppose I could write a parse script.

In that case use ParseTree like Eric suggested. Here is something that
probably does about what you want (sorry if I ruined your fun, but
this seemed like an interesting problem):

require ‘enumerator’
require ‘parse_tree’

class MethodParams
attr_reader :parsed, :methods
def initialize(klass)
@parsed = ParseTree.new.parse_tree(klass)
@methods = {}
@parsed[0].select {|i| i.respond_to?(:[]) and i[0] == :defn}.each do
|i|
if i[2][0] == :scope
@methods[i[1]] = i[2][1][1][1…-1]
end
end
end
end

if $0 == FILE
if ARGV.length < 1
puts "Usage: #$0 "
exit(1)
end
class_list = ObjectSpace.enum_for(:each_object, Class).to_a
ARGV.each do |file|
require file
end
new_classes = ObjectSpace.enum_for(:each_object, Class).to_a -
class_list
new_classes.each do |klass|
m = MethodParams.new(klass)
m.methods.keys.each do |method|
puts “The parameters for #{klass}##{method} are
#{m.methods[method].join(’,’)}”
end
end
end
END

Depending on your platform, you may have trouble with RubyInline and
ParseTree. I had to do some hackery on my Windows laptop to get the
above to work. Note that the above will only show the parameters of
instance methods on classes inside the required files.

Ryan


#8

RDoc parses this info too, maybe you could dig around in RDoc and see
how they do it?