so this is what i want to do:
class A
ATTRS = []
def list_attrs
puts ATTRS.inspect
end
end
class B < A
ATTRS = [1,2]
end
a = A.new
b = B.new
a.list_attrs
b.list_attrs
i want to create a base class with a method that plays with the ATTRS attribute of the class. in each inherited class there will be a different ATTRS array
so when i call a.list_attrs it should print an empty array and if i call b.attrs should put [1,2].
how can this be done in ruby / ruby on rails?
It is typically done with methods:
class A
def attrs
[]
end
def list_attrs
puts attrs.inspect
end
end
class B < A
def attrs
[1,2]
end
end
modf's answer works... here's another way with variables. (ATTRS is a constant in your example)
class A
def initialize
@attributes = []
end
def list_attrs
puts @attributes.inspect
end
end
class B < A
def initialize
@attributes = [1,2]
end
end
super in your initialize methods (except in the trivial case in this example), and in the correct order, too!
I don't think it's a good idea to create the same array each time a method is called. It's more natural to use class instance variables.
class A
def list_attrs; p self.class.attrs end
end
class << A
attr_accessor :attrs
end
class A
@attrs = []
end
class B < A
@attrs = [1, 2]
end
A.new.list_attrs # => []
B.new.list_attrs # => [1, 2]
You can also use constants along the line suggested in the question:
class A
def list_attrs; p self.class.const_get :ATTRS end
ATTRS = []
end
class B < A
ATTRS = [1, 2]
end
A.new.list_attrs # => []
B.new.list_attrs # => [1, 2]
