objective-c - ARC 禁止发送 'retain' 问题的显式消息

Question

我正在使用 Apple 指南中的这个非常简单的代码:

NSMutableData *receivedData;

// Create the request.
NSURLRequest *theRequest=[NSURLRequest requestWithURL:[NSURL URLWithString:@"http://www.apple.com/"]
                        cachePolicy:NSURLRequestUseProtocolCachePolicy
                    timeoutInterval:60.0];
// create the connection with the request
// and start loading the data
NSURLConnection *theConnection=[[NSURLConnection alloc] initWithRequest:theRequest delegate:self];
if (theConnection) {
    // Create the NSMutableData to hold the received data.
    // receivedData is an instance variable declared elsewhere.
    receivedData = [[NSMutableData data] retain];
} else {
    // Inform the user that the connection failed.
}

但是对于行 receivedData = [[NSMutableData data] retain]; Xcode 给我一个错误:PushController.m:72:25: ARC forbids explicit message send of 'retain'

如何处理？我正在使用 Xcode 4.4.1

Answer 1

您目前正在使用 ARC 为您引用计数。 (ARC 是“自动引用计数”，iOS 5 的一项新功能)。因此您不需要手动保留或释放。您可以通过执行以下操作一起删除保留调用或关闭 ARC:

单击左侧导航 View 中的项目名称，转到 Targets -> Build Phases 并将 -fno-objc-arc 添加到任何相关的“compiler flags”文件。

See here for info on removing.

See here for basic info on ARC.