Ruby Metaprogramming: dynamic instance variable names

ruby metaprogramming instance-variables

Andrew · Jul 19, 2011 · Viewed 47.6k times · Source

Let's say I have the following hash:

{ :foo => 'bar', :baz => 'qux' }

How could I dynamically set the keys and values to become instance variables in an object...

class Example
  def initialize( hash )
    ... magic happens here...
  end
end

... so that I end up with the following inside the model...

@foo = 'bar'
@baz = 'qux'

Answer

The method you are looking for is instance_variable_set. So:

hash.each { |name, value| instance_variable_set(name, value) }

Or, more briefly,

hash.each &method(:instance_variable_set)

If your instance variable names are missing the "@" (as they are in the OP's example), you'll need to add them, so it would be more like:

hash.each { |name, value| instance_variable_set("@#{name}", value) }