CODEWITHSUNDEEP
ruby
Bobby Tables
Bobby Tables

Reputation: 1184

Dynamic Method Naming

I want to be able to name methods dynamically (I would not leave it up to user input to do this, but as an example):

puts ""
foo = gets
def (whatever the user inputted for foo)
end

How can I do this?

Upvotes: 2

Views: 738

Answers (2)

SwiftMango
SwiftMango

Reputation: 15284

The most commonly used approaches are: define_method, class_eval and instance_eval. Define method_missing method is also used a lot.

#An example of class_eval
class Foo
end

foo = gets.chomp
#suppose you input bar here
Foo.class_eval %Q{
  def #{foo}
    puts "This is #{foo} method you defined!"
  end
}
Foo.new.bar
#output: This is the bar method you defined!

instance_eval is used in a similar way but defined on a instance of a class. define_method is also similar:

#An example of define_method
klass = Class.new
foo = gets.chomp
#suppose you typed bar
klass.send(:define_method,foo) do
  puts "This is #{foo} method you defined!"
end
klass.new.bar
#output: This is bar method you defined!

Search "Ruby Metaprogramming" and there are many tutorials out there.

Upvotes: 0

siame
siame

Reputation: 8657

You can do this using the send method to send a message to the class, using the parameter :define_method to tell it you are going to define a new method for that class.

For example, having a class Car

class Car
end

c = Car.new

A call to c.sound brings about the error 

NoMethodError: undefined method `sound' for #<Car:0x29d9048>

But after defining the name of the method and sending it to the class:

input = "sound"

Car.send(:define_method, input) do
  puts "vroom!"
end

The call to c.sound now brings the output

vroom!

Upvotes: 3

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