Flask之Blueprint
Blueprint
Blueprint继承自_PackageBoundObject类
class Blueprint(_PackageBoundObject):
warn_on_modifications = False
_got_registered_once = False
def __init__(self, name, import_name, static_folder=None,
static_url_path=None, template_folder=None,
url_prefix=None, subdomain=None, url_defaults=None,
root_path=None):
_PackageBoundObject.__init__(self, import_name, template_folder,
root_path=root_path)
self.name = name
self.url_prefix = url_prefix
self.subdomain = subdomain
self.static_folder = static_folder
self.static_url_path = static_url_path
self.deferred_functions = []
if url_defaults is None:
url_defaults = {}
self.url_values_defaults = url_defaults除了Blueprint名称和导入的模块名，其他参数都有默认值，因此Blueprint可以这样初始化：
# -*- coding: utf-8 -*-
from flask import Blueprint
auth = Blueprint("auth", __name__)
import viewsBlueprint实例创建之后，需要调用Flask.register_blueprint()进行注册，我们来分析这个函数的处理流程：
def register_blueprint(self, blueprint, **options):
"""Registers a blueprint on the application.
.. versionadded:: 0.7
"""
first_registration = False
if blueprint.name in self.blueprints:
assert self.blueprints[blueprint.name] is blueprint, \
'A blueprint\'s name collision occurred between %r and ' \
'%r. Both share the same name "%s". Blueprints that ' \
'are created on the fly need unique names.' % \
(blueprint, self.blueprints[blueprint.name], blueprint.name)
else:
self.blueprints[blueprint.name] = blueprint
self._blueprint_order.append(blueprint)
first_registration = True
blueprint.register(self, options, first_registration)继续分析Blueprint.register()处理流程：
def register(self, app, options, first_registration=False):
"""Called by :meth:`Flask.register_blueprint` to register a blueprint
on the application. This can be overridden to customize the register
behavior. Keyword arguments from
:func:`~flask.Flask.register_blueprint` are directly forwarded to this
method in the `options` dictionary.
"""
self._got_registered_once = True
state = self.make_setup_state(app, options, first_registration)
if self.has_static_folder:
state.add_url_rule(self.static_url_path + '/',
view_func=self.send_static_file,
endpoint='static')
for deferred in self.deferred_functions:
deferred(state) BlueprintSetupState
这个类是Blueprint和Flask类之间的临时粘合剂。对象变量分别有Blueprint和Flask的引用、可选参数、url前缀等。需要注意的是，这里的可选参数是一般是调用Flask.register_blueprint()时传入的，优先级要高于Blueprint的可选参数
class BlueprintSetupState(object):
"""Temporary holder object for registering a blueprint with the
application. An instance of this class is created by the
:meth:`~flask.Blueprint.make_setup_state` method and later passed
to all register callback functions.
"""
def __init__(self, blueprint, app, options, first_registration):
#: a reference to the current application
self.app = app
#: a reference to the blueprint that created this setup state.
self.blueprint = blueprint
#: a dictionary with all options that were passed to the
#: :meth:`~flask.Flask.register_blueprint` method.
self.options = options
self.first_registration = first_registration
subdomain = self.options.get('subdomain')
if subdomain is None:
subdomain = self.blueprint.subdomain
self.subdomain = subdomain
url_prefix = self.options.get('url_prefix')
if url_prefix is None:
url_prefix = self.blueprint.url_prefix
#: The prefix that should be used for all URLs defined on the
#: blueprint.
self.url_prefix = url_prefix
#: A dictionary with URL defaults that is added to each and every
#: URL that was defined with the blueprint.
self.url_defaults = dict(self.blueprint.url_values_defaults)
self.url_defaults.update(self.options.get('url_defaults', ()))
def add_url_rule(self, rule, endpoint=None, view_func=None, **options):
"""A helper method to register a rule (and optionally a view function)
to the application. The endpoint is automatically prefixed with the
blueprint's name.
"""
if self.url_prefix:
rule = self.url_prefix + rule
options.setdefault('subdomain', self.subdomain)
if endpoint is None:
endpoint = _endpoint_from_view_func(view_func)
defaults = self.url_defaults
if 'defaults' in options:
defaults = dict(defaults, **options.pop('defaults'))
self.app.add_url_rule(rule, '%s.%s' % (self.blueprint.name, endpoint),
view_func, defaults=defaults, **options)
初始化有几个地方需要注意（下面的可选参数都是调用Flask.register_blueprint()时传进来的）：
- 如果可选参数中存在"url_prefix"，则以可选参数为准，否则以Blueprint自带的"url_prefix"为准
- 如果可选参数中存在"subdomain"，则以可选参数为准，否则以Blueprint自带的"subdomain"为准
BlueprintSetupState唯一对外提供的方法是 def add_url_rule(self, rule, endpoint=None, view_func=None, **options)，该方法对url做些处理后，最终还是调用Flask的add_url_rule()来添加路由规则。这里我们之间查看Flask.add_url_rule()方法如何处理的：
class Flask(_PackageBoundObject):
@setupmethod
def add_url_rule(self, rule, endpoint=None, view_func=None, **options):
if endpoint is None:
endpoint = _endpoint_from_view_func(view_func)
options['endpoint'] = endpoint
methods = options.pop('methods', None)
# if the methods are not given and the view_func object knows its
# methods we can use that instead. If neither exists, we go with
# a tuple of only ``GET`` as default.
if methods is None:
methods = getattr(view_func, 'methods', None) or ('GET',)
if isinstance(methods, string_types):
raise TypeError('Allowed methods have to be iterables of strings, '
'for example: @app.route(..., methods=["POST"])')
methods = set(item.upper() for item in methods)
# Methods that should always be added
required_methods = set(getattr(view_func, 'required_methods', ()))
# starting with Flask 0.8 the view_func object can disable and
# force-enable the automatic options handling.
provide_automatic_options = getattr(view_func,
'provide_automatic_options', None)
if provide_automatic_options is None:
if 'OPTIONS' not in methods:
provide_automatic_options = True
required_methods.add('OPTIONS')
else:
provide_automatic_options = False
# Add the required methods now.
methods |= required_methods
rule = self.url_rule_class(rule, methods=methods, **options)
rule.provide_automatic_options = provide_automatic_options
self.url_map.add(rule)
if view_func is not None:
old_func = self.view_functions.get(endpoint)
if old_func is not None and old_func != view_func:
raise AssertionError('View function mapping is overwriting an '
'existing endpoint function: %s' % endpoint)
self.view_functions[endpoint] = view_func- 如果没有提供endpoint，则获取路由函数的名称作为路由规则的endpoint（这里说明，每个路由规则必然带有一个endpoint）
- 如果没有提供可选参数“methods”，则默认以GET方法来装饰，所有方法转换为大写
- 生成路由规则rule，并且添加到url_map中
- 如果路由规则处理函数不为空，则添加到view_functions字典中，key就是endpoint，value则是路由处理函数