Using Metaclass to implement a streamlined ORM framework

Archive:

1 #-*-coding:utf-8-*-2 classField (object):3 4     def __init__(self, Name, Column_type):5Self.name =name6Self.column_type =Column_type7 8     def __str__(self):9         return '<%s:%s>'% (self.__class__.__name__, Self.name)Ten classStringfield (Field): One  A     def __init__(self, name): -Super (Stringfield, self).__init__(Name,'varchar (+)') -  the classIntegerfield (Field): -  -     def __init__(self, name): -Super (Integerfield, self).__init__(Name,'bigint') + classModelmetaclass (type): -  +     def __new__(CLS, name, bases, attrs): A         ifname=='Model': at             returnType.__new__(CLS, name, bases, Attrs) -         Print('Found Model:%s'%name) -mappings =dict () -          forKvinchAttrs.items (): -             ifisinstance (V, Field): -                 Print('Found Mapping:%s ==>%s'%(k, v)) inMAPPINGS[K] =v -          forKinchMappings.keys (): to Attrs.pop (k) +attrs['__mappings__'] = Mappings#Saving mappings for properties and columns -attrs['__table__'] = Name#Assuming that the table name and class name match the         returnType.__new__(CLS, name, bases, Attrs) * classModel (Dict, metaclass=modelmetaclass): $ Panax Notoginseng     def __init__(Self, * *kw): -Super (Model, self).__init__(**kw) the  +     def __getattr__(self, key): A         Try: the             returnSelf[key] +         exceptKeyerror: -             RaiseAttributeerror (R"' Model ' object has no attribute '%s '"%key) $  $     def __setattr__(self, Key, value): -Self[key] =value -  the     defSave (self): -Fields = []Wuyiparams = [] theargs = [] -          forKvinchSelf.__mappings__. Items (): Wu fields.append (v.name) -Params.append ('?') About Args.append (GetAttr (self, k, None)) $sql ='insert into%s (%s) values (%s)'% (self.__table__,','. Join (Fields),','. Join (params)) -         Print('SQL:%s'%sql) -         Print('ARGS:%s'%str (args)) - classUser (Model): A     #to define a property-to-column mapping for a class: +id = Integerfield ('ID') theName = Stringfield ('username') -email = Stringfield ('Email') $Password = Stringfield ('Password') the #Create an instance: theU = User (id=12345, name='Michael', email='[email protected]', password='my-pwd') the #Save to database: theU.save ()

The results are as follows:

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 ', ' [email protected] ', ' my-pwd ']
[Finished in 0.2s]

Using Metaclass to implement a streamlined ORM framework