Ruby将参数传递给方法

Question

I would like to add a method to a class C

class C
end

I defined a proc:

impl = proc{|x,y| puts "x=#{x} - y=#{y}"}

I added the proc to the class as a method foo :

C.send(:define_method, :foo, lambda do |args = impl.parameters.map { |arg| arg[1] }|
        puts "foo is called"
        impl.call(args)
    end
 )

When I call foo as C.new.foo(1,2) , I get an error:

ArgumentError: wrong number of arguments (2 for 0..1)

To avoid this, I need to call foo like C.new.foo([1,2]) . Someone can tell me how to avoid this problem?

Answer 1

Answering the question stated:

C.send(:define_method, :foo, lambda do |*args|
  args = impl.parameters.map(&:last) if args.empty?
  puts "foo is called, args are: #{args.inspect}"
  impl.call(*args)
end)
C.new.foo(1,2)
#⇒ foo is called, args are: [1, 2]
#  x=1 - y=2

Since you want to pass an arbitrary amount of parameters to the method, the lambda should receive splat argument.

Also, defaulting to impl.parameters.map(&:last) makes not much sense, since the defaults will be symbols [:x, :y] .