dhulihan dhulihan - 6 months ago 20
Ruby Question

Dynamically Create Class Attributes with attr_accessor

In Ruby, is there a way to dynamically add a instance variable to a class? For Example:

class MyClass

def initialize
create_attribute("name")
end

def create_attribute(name)
attr_accessor name.to_sym
end

end

o = MyClass.new
o.name = "Bob"
o.name

Answer

One way (there are others) is to use instance_variable_set and instance_variable_get as so:

class Test
    def create_method( name, &block )
        self.class.send( :define_method, name, &block )
    end

    def create_attr( name )
        create_method( "#{name}=".to_sym ) { |val| 
            instance_variable_set( "@" + name, val)
        }

        create_method( name.to_sym ) { 
            instance_variable_get( "@" + name ) 
        }
    end
end

t = Test.new
t.create_attr( "bob" )
t.bob = "hello"
puts t.bob