ios - 带有完成处理程序的函数，执行何时完成？
<p><p>假设我有以下函数定义:</p>
<pre><code>func validResponse(data: Data?, response: URLResponse?, error: Error?, viewController: UIViewController, context: String?, withCompletion completion: @escaping (Bool?, String?) -> ()) {
</code></pre>
<p>然后在这个函数里面我有:</p>
<pre><code>case 500: //internal server error
debug.log(tag: "NetworkHelper", content: "\(response!.url!.path) returned 500. Payload: \(NSString(data: data!, encoding: String.Encoding.utf8.rawValue)!)")
completion(true, "500, internal server error")
print("do something")
</code></pre>
<p><code>print("do something")</code> 会被执行吗？我不想这样做，但想知道在所有完成调用之后是否应该包含 <code>return</code> ？</p>
<p>编辑:假设我有一堆这样的代码:</p>
<pre><code>if data == nil {
debug.log(tag: "NetworkHelper", content: "Error, did not receive any data on \(response!.url!.path)")
completion(false, "No data was received from the server")
}
if error != nil {
debug.log(tag: "NetworkHelper", content: "Error, calling GET on \(response!.url!.path)")
debug.log(tag: "NetworkHelper", content: error!.localizedDescription)
completion(false, genericError)
}
</code></pre>
<p>是否需要在每次 <code>completion</code> 调用后调用 return？</p></p>
<br><hr><h1><strong>Best Answer-推荐答案</ strong></h1><br>
<p><p>完成只是功能。如果你想在调用这个函数之后执行一些东西，你只需在完成调用之后添加这个代码。如果你不想在完成后调用任何代码，就不要写这段代码。</p>
<p>你应该使用 <em>guard</em> 来检查 nil 大小写:</p>
<pre><code>guard let data = data else { return }
debug.log(tag: "NetworkHelper", content: "Error, did not receive any data on \(response!.url!.path)")
completion(false, "No data was received from the server")
</code></pre></p>
<p style="font-size: 20px;">关于ios - 带有完成处理程序的函数，执行何时完成？，我们在Stack Overflow上找到一个类似的问题：
<a href="https://stackoverflow.com/questions/45141136/" rel="noreferrer noopener nofollow" style="color: red;">
https://stackoverflow.com/questions/45141136/
</a>
</p>
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