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
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
maybe ,
instance_variable_set(name,value)
is what your want!
eg:
class Mclass
def show_variables
puts self.class.instance_variables
end
end
Mclass.instance_variable_set(:@test,1)
o=Mclass.new
o.show_variables
you know, class is object too.
Made a mess of answering @ericso's comment/question in another comment, so here it is in an answer - a module which I use (based on @ReeseMoore's code) to do this & set instance vars, if necessary:
# adds ability to dynamically create instance vars & attr_accessors
module Attributable
def create_method(name, &block)
self.class.send(:define_method, name.to_sym, &block)
end
def create_setter(m)
create_method("#{m}=".to_sym) { |v| instance_variable_set("@#{m}", v) }
end
def create_getter(m)
create_method(m.to_sym) { instance_variable_get("@#{m}") }
end
def set_attr(method, value)
create_setter method
send "#{method}=".to_sym, value
create_getter method
end
end
