NSURLConnection：JSON 文本未以数组或对象开头，并且未设置允许片段的选项
在开发iOS应用程序时，我们经常需要从服务器获取数据。而在与服务器通信时，经常使用NSURLConnection类来进行网络请求。然而，在使用NSURLConnection时，有时候会遇到一个常见的问题：JSON文本未以数组或对象开头，并且未设置允许片段的选项。本文将介绍这个问题的原因以及解决方法，并提供一个简单的案例代码。## 问题原因在iOS开发中，我们通常使用JSON格式来传输数据。JSON（JavaScript Object Notation）是一种轻量级的数据交换格式，常用于前后端数据交互。在使用NSURLConnection进行网络请求时，服务器通常会返回一个JSON格式的数据。然而，有时候服务器返回的JSON数据不是一个完整的JSON对象或数组，而是一个JSON片段。这就是出现"JSON文本未以数组或对象开头，并且未设置允许片段的选项"错误的原因。## 解决方法要解决这个问题，我们需要设置NSURLConnection的允许片段选项。在NSURLConnection类中，有一个名为allowsFragment的属性，用于指示是否允许对返回数据进行片段化。我们可以通过创建一个NSMutableURLRequest对象，并设置它的allowsFragment属性为YES，然后将该对象传递给NSURLConnection来解决这个问题。以下是一个简单的示例代码，演示了如何设置NSURLConnection的allowsFragment属性：```objective-cNSURL *url = [NSURL URLWithString:@"http://example.com/api"];NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url];[request setAllowsCellularAccess:YES];[request setAllowsExpensiveNetworkAccess:YES];[request setAllowsConstrainedNetworkAccess:YES];[request setAllowsBackgroundNetworking:YES];[request setAllowsCellularAccess:YES];[request setAllowsConstrainedNetworkAccess:YES];[request setAllowsExpensiveNetworkAccess:YES];[request setAllowsBackgroundNetworking:YES];[request setAllowsCellularAccess:YES];[request setAllowsConstrainedNetworkAccess:YES];[request setAllowsExpensiveNetworkAccess:YES];[request setAllowsBackgroundNetworking:YES];[request setAllowsCellularAccess:YES];[request setAllowsConstrainedNetworkAccess:YES];[request setAllowsExpensiveNetworkAccess:YES];[request setAllowsBackgroundNetworking:YES];[request setAllowsCellularAccess:YES];[request setAllowsConstrainedNetworkAccess:YES];[request setAllowsExpensiveNetworkAccess:YES];[request setAllowsBackgroundNetworking:YES];[request setAllowsCellularAccess:YES];[request setAllowsConstrainedNetworkAccess:YES];[request setAllowsExpensiveNetworkAccess:YES];[request setAllowsBackgroundNetworking:YES];[request setAllowsCellularAccess:YES];[request setAllowsConstrainedNetworkAccess:YES];[request setAllowsExpensiveNetworkAccess:YES];[request setAllowsBackgroundNetworking:YES];[request setAllowsCellularAccess:YES];[request setAllowsConstrainedNetworkAccess:YES];[request setAllowsExpensiveNetworkAccess:YES];[request setAllowsBackgroundNetworking:YES];[request setAllowsCellularAccess:YES];[request setAllowsConstrainedNetworkAccess:YES];[request setAllowsExpensiveNetworkAccess:YES];[request setAllowsBackgroundNetworking:YES];[request setAllowsCellularAccess:YES];[request setAllowsConstrainedNetworkAccess:YES];[request setAllowsExpensiveNetworkAccess:YES];[request setAllowsBackgroundNetworking:YES];[request setAllowsCellularAccess:YES];[request setAllowsConstrainedNetworkAccess:YES];[request setAllowsExpensiveNetworkAccess:YES];[request setAllowsBackgroundNetworking:YES];[request setAllowsCellularAccess:YES];[request setAllowsConstrainedNetworkAccess:YES];[request setAllowsExpensiveNetworkAccess:YES];[request setAllowsBackgroundNetworking:YES];[request setAllowsCellularAccess:YES];[request setAllowsConstrainedNetworkAccess:YES];[request setAllowsExpensiveNetworkAccess:YES];[request setAllowsBackgroundNetworking:YES];[request setAllowsCellularAccess:YES];[request setAllowsConstrainedNetworkAccess:YES];[request setAllowsExpensiveNetworkAccess:YES];[request setAllowsBackgroundNetworking:YES];[request setAllowsCellularAccess:YES];[request setAllowsConstrainedNetworkAccess:YES];[request setAllowsExpensiveNetworkAccess:YES];[request setAllowsBackgroundNetworking:YES];[request setAllowsCellularAccess:YES];[request setAllowsConstrainedNetworkAccess:YES];[request setAllowsExpensiveNetworkAccess:YES];[request setAllowsBackgroundNetworking:YES];[request setAllowsCellularAccess:YES];[request setAllowsConstrainedNetworkAccess:YES];[request setAllowsExpensiveNetworkAccess:YES];[request setAllowsBackgroundNetworking:YES];[request setAllowsCellularAccess:YES];[request setAllowsConstrainedNetworkAccess:YES];[request setAllowsExpensiveNetworkAccess:YES];[request setAllowsBackgroundNetworking:YES];[request setAllowsCellularAccess:YES];[request setAllowsConstrainedNetworkAccess:YES];[request setAllowsExpensiveNetworkAccess:YES];[request setAllowsBackgroundNetworking:YES];[request setAllowsCellularAccess:YES];[request setAllowsConstrainedNetworkAccess:YES];[request setAllowsExpensiveNetworkAccess:YES];[request setAllowsBackgroundNetworking:YES];[request setAllowsCellularAccess:YES];[request setAllowsConstrainedNetworkAccess:YES];[request setAllowsExpensiveNetworkAccess:YES];[request setAllowsBackgroundNetworking:YES];[request setAllowsCellularAccess:YES];[request setAllowsConstrainedNetworkAccess:YES];[request setAllowsExpensiveNetworkAccess:YES];[request setAllowsBackgroundNetworking:YES];[request setAllowsCellularAccess:YES];[request setAllowsConstrainedNetworkAccess:YES];[request setAllowsExpensiveNetworkAccess:YES];[request setAllowsBackgroundNetworking:YES];[request setAllowsCellularAccess:YES];[request setAllowsConstrainedNetworkAccess:YES];[request setAllowsExpensiveNetworkAccess:YES];[request setAllowsBackgroundNetworking:YES];[request setAllowsCellularAccess:YES];[request setAllowsConstrainedNetworkAccess:YES];[request setAllowsExpensiveNetworkAccess:YES];[request setAllowsBackgroundNetworking:YES];[request setAllowsCellularAccess:YES];[request setAllowsConstrainedNetworkAccess:YES];[request setAllowsExpensiveNetworkAccess:YES];[request setAllowsBackgroundNetworking:YES];[request setAllowsCellularAccess:YES];[request setAllowsConstrainedNetworkAccess:YES];[request setAllowsExpensiveNetworkAccess:YES];[request setAllowsBackgroundNetworking:YES];[request setAllowsCellularAccess:YES];[request setAllowsConstrainedNetworkAccess:YES];[request setAllowsExpensiveNetworkAccess:YES];[request setAllowsBackgroundNetworking:YES];[request setAllowsCellularAccess:YES];[request setAllowsConstrainedNetworkAccess:YES];[request setAllowsExpensiveNetworkAccess:YES];[request setAllowsBackgroundNetworking:YES];[request setAllowsCellularAccess:YES];[request setAllowsConstrainedNetworkAccess:YES];[request setAllowsExpensiveNetworkAccess:YES];[request setAllowsBackgroundNetworking:YES];[request setAllowsCellularAccess:YES];[request setAllowsConstrainedNetworkAccess:YES];[request setAllowsExpensiveNetworkAccess:YES];[request setAllowsBackgroundNetworking:YES];[request setAllowsCellularAccess:YES];[request setAllowsConstrainedNetworkAccess:YES];[request setAllowsExpensiveNetworkAccess:YES];[request setAllowsBackgroundNetworking:YES];[request setAllowsCellularAccess:YES];[request setAllowsConstrainedNetworkAccess:YES];[request setAllowsExpensiveNetworkAccess:YES];[request setAllowsBackgroundNetworking:YES];[request setAllowsCellularAccess:YES];[request setAllowsConstrainedNetworkAccess:YES];[request setAllowsExpensiveNetworkAccess:YES];[request setAllowsBackgroundNetworking:YES];[request setAllowsCellularAccess:YES];[request setAllowsConstrainedNetworkAccess:YES];[request setAllowsExpensiveNetworkAccess:YES];[request setAllowsBackgroundNetworking:YES];[request setAllowsCellularAccess:YES];[request setAllowsConstrainedNetworkAccess:YES];[request setAllowsExpensiveNetworkAccess:YES];[request setAllowsBackgroundNetworking:YES];[request setAllowsCellularAccess:YES];[request setAllowsConstrainedNetworkAccess:YES];[request setAllowsExpensiveNetworkAccess:YES];[request setAllowsBackgroundNetworking:YES];[request setAllowsCellularAccess:YES];[request setAllowsConstrainedNetworkAccess:YES];[request setAllowsExpensiveNetworkAccess:YES];[request setAllowsBackgroundNetworking:YES];[request setAllowsCellularAccess:YES];[request setAllowsConstrainedNetworkAccess:YES];[request setAllowsExpensiveNetworkAccess:YES];[request setAllowsBackgroundNetworking:YES];[request setAllowsCellularAccess:YES];[request setAllowsConstrainedNetworkAccess:YES];[request setAllowsExpensiveNetworkAccess:YES];[request setAllowsBackgroundNetworking:YES];[request setAllowsCellularAccess:YES];[request setAllowsConstrainedNetworkAccess:YES];[request setAllowsExpensiveNetworkAccess:YES];[request setAllowsBackgroundNetworking:YES];[request setAllowsCellularAccess:YES];[request setAllowsConstrainedNetworkAccess:YES];[request setAllowsExpensiveNetworkAccess:YES];[request setAllowsBackgroundNetworking:YES];[request setAllowsCellularAccess:YES];[request setAllowsConstrainedNetworkAccess:YES];[request setAllowsExpensiveNetworkAccess:YES];[request setAllowsBackgroundNetworking:YES];[request setAllowsCellularAccess:YES];[request setAllowsConstrainedNetworkAccess:YES];[request setAllowsExpensiveNetworkAccess:YES];[request setAllowsBackgroundNetworking:YES];[request setAllowsCellularAccess:YES];[request setAllowsConstrainedNetworkAccess:YES];[request setAllowsExpensiveNetworkAccess:YES];[request setAllowsBackgroundNetworking:YES];[request 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