Feature #18948
closedAdd `with_private_method` option to `private_constant`
Description
Problem¶
I have the following code:
module M1
CONST = 'CONST'.freeze
end
module M2
def self.included(base)
base.include M1
base.include InstanceMethods
end
module InstanceMethods
def const?(value)
M1::CONST == value
end
end
end
class C
include M2
end
C.new.const?('CONST') # => true
M2
module "inherits" M1
module using included
hook. This code works, but I prefer making constants private. However, when I add private_constant :CONST
to M1
then the code doesn't work anymore since we cannot refer M1::CONST
.
Workaround¶
One way to solve this is to define method that just returns the private constant.
# Refined version of M1 with `const` method
module M1
CONST = 'CONST'.freeze
private_constant :CONST
private
def const
CONST
end
end
# Refined version of M2, using `const` method inherited from M1
module M2
def self.included(base)
base.include M1
base.include InstanceMethods
end
module InstanceMethods
def const?(value)
const == value
end
end
end
This works anyway, but defining private method for every private constant could be cumbersome.
Solution¶
So my suggestion here is to add with_private_method
option to private_constant
method. The auto-generated private method has the same name as the given constant and just returns it. So we can do the following:
module M1
CONST = 'CONST'.freeze
private_constant :CONST, with_private_method: true
end
Now we can access CONST
with const
method. This makes is possible to refer private constants through private methods more easily, that helps some code like my example.
Updated by mame (Yusuke Endoh) over 2 years ago
How about calling include M1
in M2::InstanceMethods
?
module M1
CONST = 'CONST'.freeze
private_constant :CONST
end
module M2
def self.included(base)
base.include InstanceMethods
end
module InstanceMethods
include M1
def const?(value)
CONST == value
end
end
end
class C
include M2
end
C.new.const?('CONST') # => true
Updated by okuramasafumi (Masafumi OKURA) over 2 years ago
In a real world code I'm facing, M1
contains lots of other methods so including it in InstanceMethods
causes confusion.
I pushed my code on GitHub.
https://github.com/okuramasafumi/alba/blob/jsonapi/lib/alba/resource.rb#L299-L301
https://github.com/okuramasafumi/alba/blob/jsonapi/lib/alba/jsonapi.rb#L30-L43
Updated by jeremyevans0 (Jeremy Evans) over 2 years ago
okuramasafumi (Masafumi OKURA) wrote in #note-2:
In a real world code I'm facing,
M1
contains lots of other methods so including it inInstanceMethods
causes confusion.
You should be able to work around this by making sure the M1 namespace surrounds the method in question, so unqualified constant lookup works:
module M1
CONST = 'CONST'.freeze
private_constant :CONST
end
module M2
def self.included(base)
base.include M1
base.include InstanceMethods
end
module ::M1
module ::M2::InstanceMethods
def const?(value)
CONST == value
end
end
end
end
class C
include M2
end
C.new.const?('CONST') # => true
I don't think this need is common enough to support in private_constant
. If you really need a private method defined that returns the constant value, you can always define it manually.
Updated by okuramasafumi (Masafumi OKURA) 10 months ago
I'm convinced by Jeremy's argument. Please someone close this issue.
Updated by jeremyevans0 (Jeremy Evans) 10 months ago
- Status changed from Open to Closed