This project wants to implement a mixin library like ruby's module.
In object-oriented programming languages, a mixin is a class which contains a combination of methods from other classes. How such a combination is done depends on the language, but it is not by inheritance. If a combination contains all methods of combined classes it is equivalent to multiple inheritance. For more information, please refer to this wiki: http://en.wikipedia.org/wiki/Mixin
install it from pip:
pip install mixin
In fact, the pymix package only has one file, it is mixin.py, so you can also copy it directly to your project directory.
Import the Mixin class and mixin decorator from the mixin module:
>>> from mixin import Mixin, mixin
The user's mixin class should always inherit from the Mixin class:
>>> class MixinA(Mixin):
... def func_mixin_a(self):
... return 'do_func_mixin_a'
...
and then use the mixin decorator to add the mixin to a class:
>>> @mixin(MixinA)
... class A(object): pass
...
>>> a = A()
>>> a.func_mixin_a()
'do_func_mixin_a'
The mixin should not be inherited by another class:
>>> class MixinA(Mixin): pass
...
>>> class A(MixinA): pass
...
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "mixin.py", line 58, in __new__
raise InheritMixinError(clsname)
__main__.InheritMixinError: A
But you can add a mixin to another mixin:
>>> class MixinA(Mixin):
... def func_mixin_a(self):
... return 'do_func_mixin_a'
...
>>> @mixin(MixinA)
... class MixinB(Mixin):
... def func_mixin_b(self):
... return 'do_func_mixin_b'
...
Then add the MixinB to a normal class
>>> @mixin(MixinB)
... class M(object): pass
...
>>> m = M()
>>> m.func_mixin_a()
'do_func_mixin_a'
>>> m.func_mixin_b()
'do_func_mixin_b'
>>> class MixinA(Mixin): pass
...
>>> a = MixinA()
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "mixin.py", line 44, in mixin_new
raise InstantiationMixinError(cls)
__main__.InstantiationMixinError: <class '__main__.MixinA'>
Two kind of methods to inherit multi mixins, one is writing multi mixins in one decorator:
>>> class MixinA(Mixin): pass
...
>>> class MixinB(Mixin): pass
...
>>> @mixin(MixinA, MixinB)
... class M(object): pass
...
Another is using multi decorators:
>>> @mixin(MixinA)
... @mixin(MixinB)
... class M(object): pass
...
When writes multi mixins to one decorator, the left mixin has a higher priority
>>> class MixinA(Mixin):
... def mixin_func(self):
... return 'do_mixin_a'
...
>>> class MixinB(Mixin):
... def mixin_func(self):
... return 'do_mixin_b'
...
>>> @mixin(MixinA, MixinB)
... class M(object): pass
...
>>> m = M()
>>> m.mixin_func()
'do_mixin_a'
When writes multi mixins in multi decorators, the up mixin has a higher priority:
>>> @mixin(MixinA)
... @mixin(MixinB)
... class M(object): pass
...
>>> m = M()
>>> m.mixin_func()
'do_mixin_a'
If the class has a funciton which has the same name as the mixin, the mixin method will be overwrite:
>>> class MixinA(Mixin):
... def mixin_func(self):
... return 'do_mixin_a'
...
>>> @mixin(MixinA)
... class A(object):
... def mixin_func(self):
... return 'real_class_mixin_a'
...
>>> a = A()
>>> a.mixin_func()
'real_class_mixin_a'
If a class has a father class, and the father class has a same name method as the mixin, the father class' method will be overwrite:
>>> class MixinA(Mixin):
... def mixin_func(self):
... return 'do_mixin_a'
...
>>> class Father(object):
... def mixin_func(self):
... return 'father_mixin'
...
>>> @mixin(MixinA)
... class A(Father): pass
...
>>> a=A()
>>> a.mixin_func()
'do_mixin_a'
Tested on python2.6, python2.7 and python3.4
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