ORM实现
from mysql_client import MySQLClient
class Field:
def __init__(self, name, column_type, primary_key, default):
self.name = name
self.column_type = column_type
self.primary_key = primary_key
self.default = default
class Integerfield(Field):
def __init__(self, name, column_type='int', primary_key=False, default=None):
super().__init__(name, column_type, primary_key, default)
class Stringfield(Field):
def __init__(self, name, column_type='varchar(64)', primary_key=False, default=None):
super().__init__(name, column_type, primary_key, default)
class OrmMetaClass(type):
def __new__(cls, class_name, class_bases, class_dict):
if class_name == 'Models':
return type.__new__(cls, class_name, class_bases, class_dict)
table_name = class_dict.get('table_name', class_name)
mappings = {}
primary_key = None
for key, value in class_dict.items():
if isinstance(value, Field):
mappings[key] = value
if value.primary_key:
if primary_key:
raise TypeError('只能有一个主键!')
primary_key = value.name
for k in mappings.keys():
class_dict.pop(k)
if not primary_key:
raise TypeError('必须有一个主键!')
class_dict['tablel_name'] = table_name
class_dict['primary_key'] = primary_key
class_dict['mappings'] = mappings
return type.__new__(cls, class_name, class_bases, class_dict)
class Models(metaclass=OrmMetaClass):
def __init__(self, **kwargs):
for name, value in kwargs.items():
setattr(self, name, value)
@classmethod
def orm_select(cls, **kwargs):
mysql = MySQLClient()
if not kwargs:
sql='select * from %s' % cls.table_name
res = mysql.my_select(sql)
else:
key = list(kwargs.keys())[0]
value = kwargs.get(key)
sql = 'select * from %s where %s=?' % (cls.table_name, key)
sql.replace('?', '%s')
res = mysql.my_select(sql, value)
return res
mysql.close()
def orm_insert(self):
mysql = MySQLClient()
keys = []
values = []
args = []
for k, v in self.mappings.items():
if not v.primary_key:
keys.append(k)
values.append(getattr(self, v.name, v.default))
args.append('?')
sql = 'insert into %s(%s) values (%s)' % (
self.table_name,
','.join(keys),
','.join(args)
)
sql = sql.replace('?', '%s')
mysql.my_execute(sql, values)
mysql.close()
def orm_update(self):
mysql = MySQLClient()
keys = []
values = []
primary_key = None
for k, v in self.mappings.item():
if v.primary_key:
primary_key = v.name + '= %s' % getattr(self, v.name)
else:
keys.append(v.name + '=?')
values.append(getattr(self, v.name))
sql = 'update %s set %s where %s' % (
self.table_name,
','.join(keys),
primary_key
)
sql = sql.replace('?', '%s')
mysql.my_execute(sql, values)
mysql.close()
class User(Models):
user_id = Integerfield(name='user_id', primary_key=True)
user_name = Stringfield(name='user_name')
pwd = Stringfield(name='pwd')
