In Javascript I could do this.
var a = {};
a.f1 = function(){};
How can I do this in Ruby?
Update.
In JS code, a is an object instantiated without class. And function(){} is an anonymous function, and a.f1 = adds the function to the object instance. So the function is bound to the instance only, and nothing is related to the class or similar definitions.
Ruby and JS's object models are very different, but a direct translation may look like this:
a = Object.new
def a.f1(x)
2*x
end
a.f1(5) #=> 10
You can also use the Ruby's eigenclass:
class Object
def metaclass
class << self; self; end
end
end
a = Object.new
# Also: (class << a; self; end).send(:define_method, :f1) do |x|
a.metaclass.send(:define_method, :f1) { |x| 2*x }
A warning note: you'll see this kind of code in meta-programming/monkeypatching/... but it's not usual when writing "normal" code, where other techniques (module mix-ins, mainly) apply.
Object class as a instance method f1?
foo.class.send(:define_method, :bar) do ... end
There's difference between JavaScript and other languages because JavaScript does inheritance in another way. So here's couldn't be direct analogue.
Let's pretend that {} is the A class in ruby and you create object from it
class A
end
a = A.new
And f1 function seats in some module B
module B
def f1
puts "you've extended your object"
end
end
Now you can do what you want in similar way
a.extend(B)
a.f1 #=> "you've extended your object"
