Question

我正在尝试定义一个base request handling类，以便webapp页面可以继承一些基本方法和变量，否则需要为应用程序的每个页面重复定义。一种类似django preprocessors的功能。这是我的基类，其他页面继承该基类：

class BasePage(webapp.RequestHandler):
    def __init__(self):    
        self.user = users.get_current_user()    
        self.template_values = {
                'user': self.user,       
                'environ': self,   #I don't like the idea of passing the whole environ object to a template

                ##The below three functions cannot be executed during _init_ because of absence of self.request 
                #'openid_providers': self.openid_providers(),  
                #'logout_url': self.get_logout_url(),
                #'request': self.get_request(),
            }           

    ##A sort of similar functionality like render_to_response in django
    def render_template(self, template_name, values = None, *args, **kwargs):
        #PATH is the directory containing the templates
        if values: 
            for value in values:  self.template_values[value] = values[value]
        self.response.out.write(template.render(PATH+template_name, self.template_values, *args, **kwargs))                 

    ##Returns request as the name suggests
    def logout_url(self):
        return users.create_logout_url(self.request.url)

    ##Returns request as the name suggests
    def request(self):
        return request

    ##Returns openid login urls        
    def openid_providers(self):
        #OPENID_POVIDERS  is a list of dictionary 
        for p in OPENID_PROVIDERS:
             p['login_url'] = users.create_login_url(self.request.get('next', '/') , p['name'], p['url'])
        return OPENID_PROVIDERS

一切正常，但我无法在初始化过程中传递一些变量，因为self.request不可用。因此，对于解决方法，我所做的是将整个自变量作为模板变量传递。

是否有其他方法可以为模板提供模板变量（request，logout_url等）？

Answer 1

比bgporter更简单的解决方案是在initialize webapp.RequestHandler方法中进行常规设置。以下是工作中的示例，我们希望在请求对象中添加类似Django的is_ajax方法：

class BaseHandler(webapp.RequestHandler):
    def initialize(self, request, response):
        super(BaseHandler, self).initialize(request, response)
        # Add a Django-like is_ajax() method to the request object
        request.is_ajax = lambda: \
            request.environ.get('HTTP_X_REQUESTED_WITH') == 'XMLHttpRequest'

在调用适当的get或post（或其他）方法之前，调用此方法，呃，用当前请求和响应对象初始化每个请求处理程序。

Answer 2

我已使用Template Method Pattern

在AppEngine代码中解决了该问题

基本上，基类看起来像：

class MyBasePage(webapp.RequestHandler):
    def __init__(self):
        # common setup/init stuff here, 
        # omitted for this discussion

    def Setup(self):
        # request handling setup code needed in both GET/POST methods, like
        # checking for user login, getting session cookies, etc.
        # omitted for this discussion

    def get(self, *args):
        self.Setup()
        # call the derived class' 'DoGet' method that actually has 
        # the logic inside it
        self.DoGet(*args)

    def post(self, *args):
        self.Setup()
        # call the derived class' 'DoPost' method 
        self.DoPost(*args)

    def DoGet(self, *args):
        ''' derived classes override this method and 
            put all of their GET logic inside. Base class does nothing.'''
        pass

    def DoPost(self, *args):
        ''' derived classes override this method and 
            put all of their POST logic inside. Base class does nothing.'''
        pass

...您的派生类通常只需要担心这些DoGet()和DoPost()方法的内容。

Google App Engine，定义预处理类

2 个答案: