How can I get the default values for named arguments for a method?

Question

Suppose I have this method:

def person(name: "calvin")
  ...
end

I want to find the default value for param name. How would I do that?

I'm not sure this is possible. Why are you looking to do this? You could declare that as a constant external to the method. — tadman, Apr 20 '15 at 17:28
See this question: http://stackoverflow.com/questions/622324/getting-argument-names-in-ruby-reflection — Casper, Apr 20 '15 at 17:37
You're right, I mean "can I do that". I looked into the Merb code, but it is hairy. I was wondering if there's a simpler way to do it. — Vlad the Impala, Apr 20 '15 at 18:21

steenslag · Accepted Answer · 2015-04-20T21:49:09.293

3

There is no list of parameter defaults, a default value is code that is executed.

def foo(t=Time.now)
  p t
end

foo  #2015-04-20 19:43:54 +0200
sleep 1
foo  #2015-04-20 19:43:55 +0200

edited Apr 20 '15 at 21:49

answered Apr 20 '15 at 17:48

steenslag

Good answer. Here's another simple example, where the default value depends on the number of times the method's been called: `@b = 0; def a(t=@b) @b += 1 end`. – Cary Swoveland Apr 20 '15 at 18:36

score 0 · Answer 2 · answered Apr 20 '15 at 17:40

0

Not sure whether this will help, but person.send(:local_variables) might be a good starting point.

answered Apr 20 '15 at 17:40

fylooi

No, it doesn't help. Neither does `method(:person).parameters #=> [[:key, :name]] `. – Cary Swoveland Apr 20 '15 at 17:44

2 Answers2