Ruby define method to return proc which makes use of an argument

Question

In Ruby, I'd like to define a method that takes an argument, which returns a proc full of methods that make use of that argument. Something like the following

def test(word)
  proc do
    def hello
      puts word
    end
  end
end

my_proc = test('hello')
my_proc.call.hello

When running this code, the local variable 'word' is undefined

To give some more context, I am trying to make use of association extensions, which allow you to provide a block of methods to an association to define extra helper methods on the association. I have some methods I'd like to use on several similar active record models with similar associations, but they only differ by a certain symbol when making calls (the name of the join table passed to through on a has_many relationship). So ideally I was thinking of making a method that accepts that symbol, which could then be used in the implementation of the association extension.

Answer 1

Your example has two problems:

1. You can't call a "proc full of methods" like that -- it'll work as an association extension, but there the block is evaluated as a module body, not called.

2. The def keyword resets the local variable scope. To get a value into a function, you can either define it using define_method instead (that block retains surrounding scope), or put the value somewhere else the function will be able to find it (a class variable, for example).

---

def test(word)
  proc do
    define_method(:hello) do
      puts word
    end
  end
end

Class.new(&test("hello")).new.hello

---

Separately, if you're defining approximately the same method on several associations, there might be a simpler path by defining them as class-level scopes.