存档:
1 # -*- coding: utf-8 -*-
2 class Field(object):
3
4 def __init__(self, name, column_type):
5 self.name = name
6 self.column_type = column_type
7
8 def __str__(self):
9 return '<%s:%s>' % (self.__class__.__name__, self.name)
10 class StringField(Field):
11
12 def __init__(self, name):
13 super(StringField, self).__init__(name, 'varchar(100)')
14
15 class IntegerField(Field):
16
17 def __init__(self, name):
18 super(IntegerField, self).__init__(name, 'bigint')
19 class ModelMetaclass(type):
20
21 def __new__(cls, name, bases, attrs):
22 if name=='Model':
23 return type.__new__(cls, name, bases, attrs)
24 print('Found model: %s' % name)
25 mappings = dict()
26 for k, v in attrs.items():
27 if isinstance(v, Field):
28 print('Found mapping: %s ==> %s' % (k, v))
29 mappings[k] = v
30 for k in mappings.keys():
31 attrs.pop(k)
32 attrs['__mappings__'] = mappings # 保存属性和列的映射关系
33 attrs['__table__'] = name # 假设表名和类名一致
34 return type.__new__(cls, name, bases, attrs)
35 class Model(dict, metaclass=ModelMetaclass):
36
37 def __init__(self, **kw):
38 super(Model, self).__init__(**kw)
39
40 def __getattr__(self, key):
41 try:
42 return self[key]
43 except KeyError:
44 raise AttributeError(r"'Model' object has no attribute '%s'" % key)
45
46 def __setattr__(self, key, value):
47 self[key] = value
48
49 def save(self):
50 fields = []
51 params = []
52 args = []
53 for k, v in self.__mappings__.items():
54 fields.append(v.name)
55 params.append('?')
56 args.append(getattr(self, k, None))
57 sql = 'insert into %s (%s) values (%s)' % (self.__table__, ','.join(fields), ','.join(params))
58 print('SQL: %s' % sql)
59 print('ARGS: %s' % str(args))
60 class User(Model):
61 # 定义类的属性到列的映射:
62 id = IntegerField('id')
63 name = StringField('username')
64 email = StringField('email')
65 password = StringField('password')
66 # 创建一个实例:
67 u = User(id=12345, name='Michael', email='test@orm.org', password='my-pwd')
68 # 保存到数据库:
69 u.save()
结果如下:
Found model: User Found mapping: id ==> <IntegerField:id> Found mapping: name ==> <StringField:username> Found mapping: email ==> <StringField:email> Found mapping: password ==> <StringField:password> SQL: insert into User (id,username,email,password) values (?,?,?,?) ARGS: [12345, 'Michael', 'test@orm.org', 'my-pwd'] [Finished in 0.2s]