I want to extend the Proc class so that its constructor can also take a hash of arguments with will be converted into methods with some meta programming construct. Something to the effect of:
p = Proc.new(this: 100, that: 200, yes: 1, no: 2) { |arg| arg.even? }
p.call(1) # => false
p.this # => 100
p.yes # => 1
I want to know the ruby way of doing something like this.
class Proc
def initialize h; @h = h end
def method_missing k; @h[k] end
def respond_to_missing?; true end
end
p = Proc.new(this: 100, that: 200, yes: 1, no: 2) { |arg| arg.even? }
p.call(1) # => false
p.this # => 100
p.yes # => 1
def method_missing(k,*args); @h.fetch(k){super}; end instead.
respond_to_missing? when defining method_missing.You can (and probably should in this case) avoid monkey patching altogether by having your own class behave like a Proc by implementing to_proc and call. For example, you could start from an OpenStruct:
require 'ostruct'
class MyFunkyClass < OpenStruct
def initialize(h, &block)
@block = block
super
end
def to_proc
@block
end
def call(*args)
@block.call(*args)
end
end
f = MyFunkyClass.new(this: 100, that: 200, yes: 1, no: 2) { |arg| arg.even? }
f.that # => 200
f.call(42) # => true
[1,2,3,4].select(&f) # => [2, 4]
&:even? works; check Symbol#to_procWithout metaprogramming:
require 'ostruct'
r = OpenStruct.new(this: 100, that: 200, yes: 1, no: 2)
def r.call(n)
n.even?
end
p r.this # 100
p r.call(1) # false
Edit: @Marc-André Lafortune had the same idea about Openstruct; his implementation is way better.
