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| @app.route('/form')
def login():
login_form = LoginForm()
1.先看自己有没有__call__然后一直找到寻源类，metaclass，调用metaclass的__call__方法(这里是FormMeta的__call__)
def __call__(cls, *args, **kwargs):
if cls._unbound_fields is None:
fields = []
for name in dir(cls):
if not name.startswith('_'):
# 获取unboundfield（1，StringField， 参数）
unbound_field = getattr(cls, name)
if hasattr(unbound_field, '_formfield'):
fields.append((name, unbound_field))
# 按照定义顺序排序
fields.sort(key=lambda x: (x[1].creation_counter, x[0]))
cls._unbound_fields = fields
if cls._wtforms_meta is None:
bases = []
for mro_class in cls.__mro__:
if 'Meta' in mro_class.__dict__:
bases.append(mro_class.Meta)
cls._wtforms_meta = type('Meta', tuple(bases), {})
return type.__call__(cls, *args, **kwargs)
1.获取定义的Field按照计数器排序绑定进unbound_field
2.调用mro继承算法，继承顺序，按照mro顺序找寻每个父类对象的Meta加入bases，（拿到所有的功能），然后生成一个继承所有meta的类并把它赋值给form的 _wtforms_meta
class Form(with_metaclass(FormMeta, BaseForm)):
Meta = DefaultMeta
3.执行type.__call__( cls, *args, **kwargs)真的call方法
这时loginform中:
{
‘__module’: ‘__main__’,
‘name’:<UnboundField>(StringField…..),
‘pwd’: <UnboundField>(PasswordField…..),
‘__doc__’: None,
‘unbound_fields’: [(‘username’,<UnboundField StringField>), (‘pwd’, …….Field)],
‘_wtforms_meta’: class.Meta,
}
2.然后执行自己的__new__方法（或继承父类的）
发现父类并没有写__new__，继承的object的。不用找了
3.再执行自己的__init__方法（或继承）
class Form(with_metaclass(FormMeta, BaseForm)):
Meta = DefaultMeta
def __init__(self, formdata=None, obj=None, prefix='', data=None, meta=None, **kwargs):
meta_obj = self._wtforms_meta()
if meta is not None and isinstance(meta, dict):
meta_obj.update_values(meta)
super(Form, self).__init__(self._unbound_fields, meta=meta_obj, prefix=prefix)
for name, field in iteritems(self._fields):
# Set all the fields to attributes so that they obscure the class
# attributes with the same names.
setattr(self, name, field)
self.process(formdata, obj, data=data, **kwargs)
1.实例化_wtforms_meta meta_obj = self._wtforms_meta()
meta的功能之一csrf验证隐藏标签，django自带csrf但flask没有，wtform可以提供（生成csrf input框）
meta_obj = self._wtforms_meta()
if meta is not None and isinstance(meta, dict):
meta_obj.update_values(meta)
如果设置了meta参数，比如loginForm(meta={})会帮助更新到wtforms_meta.
2.传入meta和field列表执行父类的构造方法
super(Form, self).__init__(self._unbound_fields, meta=meta_obj, prefix=prefix)
class BaseForm(object):
def __init__(self, fields, prefix='', meta=DefaultMeta()):
if prefix and prefix[-1] not in '-_;:/.':
prefix += '-'
self.meta = meta
self._prefix = prefix
self._fields = OrderedDict()
if hasattr(fields, 'items'):
fields = fields.items()
translations = self._get_translations()
extra_fields = []
if meta.csrf:
self._csrf = meta.build_csrf(self)
extra_fields.extend(self._csrf.setup_form(self))
for name, unbound_field in itertools.chain(fields, extra_fields):
options = dict(name=name, prefix=prefix, translations=translations)
field = meta.bind_field(self, unbound_field, options)
self._fields[name] = field
1.生成csrf的隐藏field作为extra_field
2.遍历大的field可迭代对象
3.把每个field对象实例化（调用field的bind）
def bind(self, form, name, prefix='', translations=None, **kwargs):
kw = dict(
self.kwargs,
_form=form,
_prefix=prefix,
_name=name,
_translations=translations,
**kwargs
)
return self.field_class(*self.args, **kw)
4.这时候对象有了_name和_field，开始走自己真的__new__（之前是走Unbound的）
class Field(object):
errors = tuple()
process_errors = tuple()
raw_data = None
validators = tuple()
widget = None
_formfield = True
_translations = DummyTranslations()
do_not_call_in_templates = True # Allow Django 1.4 traversal
def __new__(cls, *args, **kwargs):
if '_form' in kwargs and '_name' in kwargs:
return super(Field, cls).__new__(cls)
else:
return UnboundField(cls, *args, **kwargs)
|