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510.
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If <code>callback</code> has been called on this Deferred already, call all the callbacks that have been added to this Deferred since <code>pause</code> was called.
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type: Content of: <html><body><ul><li><p>
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如果 Deferred 的 <code>callback</code> 函数已经被调用，则调用 <code>pause</code> 被调用之后的加入的回调函数。
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Located in
howto/gendefer.xhtml:156
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511.
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Whether it was called or not, this will put this Deferred in a state where further calls to <code>addCallbacks</code> or <code>callback</code> will work as normal.
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type: Content of: <html><body><ul><li><p>
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无论 <code>pause</code> 是否被调用过， <code>unpause</code> 都会让这个 Deferred 之后的 <code>addCallbacks</code> 或 <code>callback</code> 调用回到正常状态。
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Located in
howto/gendefer.xhtml:161
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512.
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Returning Deferreds from synchronous functions
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type: Content of: <html><body><h2>
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同步函数返回 Deferred
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Located in
howto/gendefer.xhtml:168
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513.
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Sometimes you might wish to return a Deferred from a synchronous function. There are several reasons why, the major two are maintaining API compatibility with another version of your function which returns a Deferred, or allowing for the possiblity that in the future your function might need to be asynchronous.
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type: Content of: <html><body><p>
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有时，你可能想让一个同步函数返回一个 Deferred。这么做有很多理由，其中最主要的两个是：保持跟 API 中其他返回 Deferred 的函数相一致；为今后函数可能需要写成异步做准备。
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Located in
howto/gendefer.xhtml:170
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514.
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In the <a href="defer.xhtml">Using Deferreds</a> reference, we gave the following example of a synchronous function:
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type: Content of: <html><body><p>
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在前面的 <a href="defer.xhtml">Deferred 使用指南</a>中，我们给过一个同步函数的例子，如下所示：
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Located in
howto/gendefer.xhtml:176
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515.
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While we can require that callers of our function wrap our synchronous result in a Deferred using <code class="API" base="twisted.internet.defer">maybeDeferred</code>, for the sake of API compatibility it is better to return a Deferred ourself using <code class="API" base="twisted.internet">defer.succeed</code>:
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type: Content of: <html><body><p>
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虽然我们可以要求调用者将函数的同步结果用 <code class="API" base="twisted.internet.defer">maybeDeferred</code> 包装在一个 Deferred 里，但是为了 API 的兼容性，最好还是使用 <code class="API" base="twisted.internet">defer.succeed</code> 直接返回一个 Deferred。
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Located in
howto/gendefer.xhtml:182
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516.
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from twisted.internet import defer 
def immediateIsValidUser(user):
'''
Returns a Deferred resulting in true if user is a valid user, false
otherwise
'''
result = user in ["Alice", "Angus", "Agnes"]
# return a Deferred object already called back with the value of result
return defer.succeed(result)
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represents a line break.
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represents a space character.
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from twisted.internet import defer
def immediateIsValidUser(user):
'''
返回 Deferred 包含结果：真 如果 user 是有效用户，否则为 假
'''
result = user in ["Alice", "Angus", "Agnes"]
# 返回一个 Deferred 对象，已经用计算结果激活了正常回调函数处理链
return defer.succeed(result)
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Located in
howto/gendefer.xhtml:189
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517.
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There is an equivalent <code class="API" base="twisted.internet">defer.fail</code> method to return a Deferred with the errback chain already fired.
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type: Content of: <html><body><p>
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这里有个等价的 <code class="API" base="twisted.internet">defer.fail</code> 方法，返回一个 Deferred，已激活错误回调函数处理链。
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Located in
howto/gendefer.xhtml:203
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518.
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Integrating blocking code with Twisted
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type: Content of: <html><body><h2>
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用 Twisted 集成阻塞代码
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Located in
howto/gendefer.xhtml:207
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519.
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At some point, you are likely to need to call a blocking function: many functions in third party libraries will have long running blocking functions. There is no way to 'force' a function to be asynchronous: it must be written that way specifically. When using Twisted, your own code should be asynchronous, but there is no way to make third party functions asynchronous other than rewriting them.
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type: Content of: <html><body><p>
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到一定的时候，你很可能需要调用阻塞的函数——很多第三方库中都有需要长时间运行的阻塞函数。没有办法去强行把函数变为异步——那必须用特定的方式写成。当使用 Twisted 时，你自己的代码应该是异步的，但没法让第三方的函数也是异步的，除非重写。
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Translated and reviewed by
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Located in
howto/gendefer.xhtml:209
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