Question

This is hard to explain as a question but here is a code fragment:

n = "Bob"
class A
end
def A.greet
  puts "Hello #{n}"
end
A.greet

This piece of code does not work because n is only evaluated inside A.greet when it is called, rather than when I add the method.

Is there a way to pass the value of a local variable into A.greet?

What about if n was a function?

Answer 1

Use metaprogramming, specifically the define_singleton_method method. This allows you to use a block to define the method and so captures the current variables.

n = "Bob"

class A
end

A.define_singleton_method(:greet) do
  puts "Hello #{n}"
end

A.greet