Create class definitions of properties (typed and ordered) with metaclass

Revision: 18755

at October 7, 2009 16:26 by manatlan

Initial Code

import os

class _FieldBase_:
    _defines=[]
    def __init__(self,*a):
        _FieldBase_._defines.append(self)

class _FieldedMetaClass_(type):
    def __init__(cls, name, bases, dct):
        super(_FieldedMetaClass_, cls).__init__(name, bases, dct)
        if name!="Form":
            fields_to_name = dict([(slot,name) for name,slot in dct.items() if isinstance(slot,_FieldBase_)])
            cls.fields = [(fields_to_name[obj],obj ) for obj in _FieldBase_._defines]
            _FieldBase_._defines=[] # reset list !!!

class Form (object):
    __metaclass__ = _FieldedMetaClass_

    def __repr__(self):
        l=["Form '%s'"%self.__class__.__name__]
        l+=["* %-10s : %s"%(f,t.__class__.__name__) for f,t in self.fields]
        return os.linesep.join(l)

class FieldInt(_FieldBase_):
    def __init__(self,*a):
        _FieldBase_.__init__(self,a)

class FieldString(_FieldBase_):
    def __init__(self,*a):
        _FieldBase_.__init__(self,a)

class Form1(Form):
    name     = FieldString(1)
    surname  = FieldString(2)
    age      = FieldInt(3)

class Form2(Form):
    nb      = FieldInt(1)
    title   = FieldString(2)

print Form1()
print Form2()

Initial URL

Initial Description

Like Django.models, GAE.db.model or SqlAlchemy definitions

Initial Title

Create class definitions of properties (typed and ordered) with metaclass

Initial Tags

python

Initial Language

Python

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