Defining class methods with Modularity traits

Updated . Posted . Visible to the public. Repeats.

There are two ways to define a class method from a Modularity Show archive.org snapshot trait. Note that the usual caveats regarding class method visibility apply.

Using define_method

The recommended way is to define a method on your module's singleton class:

module SomeTrait
  as_trait do
    define_singleton_method :foo do
      # ...
    end
  end
end

Using def (has caveats!)

Alternatively, you can def the method on self:

module SomeTrait
  as_trait do
    def self.foo
      # ...
    end
  end
end

This is quite concise and results in faster methods than using define_method. However, you cannot use it with parametrized traits.

The following will fail:

module SomeTrait
  as_trait do |name|
    def self.foo
      puts name # will raise an error because the variable 'name' is not bound to the method body
    end
  end
end
Henning Koch
makandra.de
Say thanks
Last edit
Henning Koch
Keywords
static, method
License
Source code in this card is licensed under the MIT License.

Related cards:

Rails: When defining scopes with class methods, don't use `self`

Sometimes it is useful to define a named scope by implementing a static method with the scope's name on the scoped class. For instance, when a method should decide which existing scope should be the next link in the scope chain. Take this class fo...

Defining and using sub-classes with modularity

Given this class:

class Foo
  class Bar
  end
end

If you want to clean up this code with the modularity gem, you might try something like this:

class Foo
  does 'bar'
end

module BarTr...

Calling class methods

To call a class method (or static method) from an instance method:

class.method()

To call a class method from a class method:

method()

Using Ruby's Method objects for inspecting methods

Do you remember finding where a method is defined?

I recently learned from a senior colleague that Method objects ar...

How to call overwritten methods of parent classes in Backbone.js

When you are working with Backbone models and inheritance, at some point you want to overwrite inherited methods but call the parent's implementation, too.
In JavaScript, there is no simple "super" method like in Ruby -- so here is how to do it ...

Coffeescript: Caveat when cloning objects with fat-arrow methods

Coffeescript allows you to create classes whose methods are automatically bound to the correct this. You can do this by using a fat arrow:

class Person

  constructor: (name) ->
    @name = name

  sayHello: =>
    alert("Hello, I am #{@nam...

Hack of the day: Find all classes that define a method with a given name

If (for some reason that you don't want to ask yourself) you need to know all classes that define a method with a given name, you can do it like this:

def classes_defining_method(method_name)
  method_name = method_name.to_sym
  Objec...

Stubbed class methods in RSpec 1 remain stubbed in other examples

I encountered a bug in RSpec 1.x where stubbed class methods ("static methods") would not be unstubbed before the next example, causing it to fail. This behavior can come and go as you edit your specs, since this can change the order in which RSpe...

Using Capybara finder methods with arbitrary matching conditions

Capybara has a variety of finder methods like find_button to help you look up DOM elements. There are also matchers ...

Class methods in Coffeescript

How to define and call class methods in CoffeeScript classes:

class Foo

  @classMethod: -> 
    @otherClassMethod()
  
  instanceMethod: ->
    @otherInstanceMethod()
    @constructor.classMethod()
Posted by Henning Koch to makandra dev (2011-03-08 18:48)
This website uses short-lived cookies to improve usability.
or learn more