Create module variables in Ruby
RubyModuleClass VariablesRuby Problem Overview
Is there any way to create a variable in a module in Ruby that would behave similar to a class variable? What I mean by this is that it would be able to be accessed without initializing an instance of the module, but it can be changed (unlike constants in modules).
Ruby Solutions
Solution 1 - Ruby
Ruby natively supports class variables in modules, so you can use class variables directly, and not some proxy or pseudo-class-variables:
module Site
@@name = "StackOverflow"
def self.setName(value)
@@name = value
end
def self.name
@@name
end
end
Site.name # => "StackOverflow"
Site.setName("Test")
Site.name # => "Test"
Solution 2 - Ruby
If you do not need to call it from within an instance, you can simply use an instance variable within the module body.
module SomeModule
module_function
def param; @param end
def param= v; @param = v end
end
SomeModule.param
# => nil
SomeModule.param = 1
SomeModule.param
# => 1
The instance variable @param
will then belong to the module SomeModule
, which is an instance of the Module
class.
Solution 3 - Ruby
you can set a class instance variable in the module.
module MyModule
class << self; attr_accessor :var; end
end
MyModule.var = 'this is saved at @var'
MyModule.var
=> "this is saved at @var"
Solution 4 - Ruby
You can also initialize value within module definition:
module MyModule
class << self
attr_accessor :my_variable
end
self.my_variable = 2 + 2
end
p MyModule.my_variable