Pass a function by name in Ruby

Question

How can you pass a function by name in Ruby? (I've only been using Ruby for a few hours, so I'm still figuring things out.)

nums = [1, 2, 3, 4]

# This works, but is more verbose than I'd like    
nums.each do |i|
  puts i
end

# In JS, I could just do something like:
# nums.forEach(console.log)

# In F#, it would be something like:
# List.iter nums (printf "%A")

# In Ruby, I wish I could do something like:
nums.each puts

Can it be done similarly concisely in Ruby? Can I just reference the function by name instead of using a block?

People voting to close: Can you explain why this isn't a real question?

Is that what you're looking for? http://stackoverflow.com/questions/522720/passing-a-method-as-a-parameter-in-ruby — Glauco Vinicius, Dec 10 '12 at 21:25

score 6 · Accepted Answer · answered Dec 10 '12 at 21:33

6

You can do the following:

nums = [1, 2, 3, 4]
nums.each(&method(:puts))

This article has a good explanation of the differences between procs, blocks, and lambdas in Ruby.

answered Dec 10 '12 at 21:33

Chris Schmich

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It's also possible to specify an instance method, e.g. `nums.each(&$stderr.method(:puts))` – Chris Schmich Dec 11 '12 at 18:22

score 3 · Answer 2 · answered Dec 10 '12 at 21:34

3

Can I just reference the function by name instead of wrapping it in a block?

You aren't 'wrapping' it -- the block is the function.

If brevity is a concern, you can use brackets instead of do..end:

nums.each {|i| puts i}

answered Dec 10 '12 at 21:34

zetetic

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score 0 · Answer 3 · answered Dec 10 '12 at 21:37

0

Not out-of-the-box, although you can use method:

def invoke(enum, meth)
  enum.each { |e| method(meth).call(e) }
end

I prefer it wrapped up into a monkeypatched Enumerable.

There are other ways to go about this, too; this is kind of brute-force.

answered Dec 10 '12 at 21:37

Dave Newton

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Pass a function by name in Ruby

3 Answers3