如何在 NSStream 中使用委托?

问题描述

我是 Objective-C 的新手.我正在尝试学习如何使用 NSStream.我只是使用了 Apple 支持的简单代码.此代码应从我的桌面中的文件打开一个流，并在 iStream 调用委托时显示一条简单消息.在代码的最后，我可以看到状态是正确的，但委托永远不会被调用.我错过了什么?

I am a newbie in Objective-C. I am trying to learn how to work with NSStream. I just used simple code from Apple Support. This code should open a stream from a file in my Desktop and show a simple message when the delegate is called by iStream. At the end of the code, I can see the status is correct, but the delegate never gets called. What am I missing?

#import <Foundation/Foundation.h>

@interface MyDelegate: NSStream <NSStreamDelegate>{
}

- (void)stream:(NSStream *)stream handleEvent:(NSStreamEvent)eventCode ;

@end

@implementation MyDelegate

- (void)stream:(NSStream *)stream handleEvent:(NSStreamEvent)eventCode  {
    NSLog(@"############# in DELEGATE###############");
}

@end

int main(int argc, const char * argv[])
{
    @autoreleasepool {
        MyDelegate* myDelegate=[[MyDelegate alloc]init];
        NSInputStream* iStream= [[NSInputStream alloc] initWithFileAtPath:@"/Users/Augend/Desktop/Test.rtf"];

        [iStream setDelegate:myDelegate];

        [iStream scheduleInRunLoop:[NSRunLoop currentRunLoop]
                           forMode:NSDefaultRunLoopMode];
        [iStream open];

        NSLog(@" status:%@",(NSString*) [iStream streamError]);
    }
    return 0;
}

推荐答案

run loop 运行时间不够长，无法调用委托方法.

The run loop isn't running long enough for the delegate method to be called.

添加:

[[NSRunLoop currentRunLoop] runUntilDate:[NSDate dateWithTimeIntervalSinceNow:2.0]];

在您打开信息流之后.这仅在没有 GUI 的程序中是必需的 - 否则运行循环将为您旋转.

right after you open the stream. This is only necessary in a program without a GUI -- otherwise the run loop would be spun for you.

如果您想在退出之前绝对确定 stream:handleEvent: 已被调用，请在该方法中设置一个(全局)标志并将 runUntilDate: 放入一个测试标志的 while 循环:

If you want to be absolutely sure that stream:handleEvent: has been called before exiting, set a (global) flag in that method and put the runUntilDate: in a while loop that tests for the flag:

while( !delegateHasBeenNotified ){
     [[NSRunLoop currentRunLoop] runUntilDate:[NSDate dateWithTimeIntervalSinceNow:0.5]];
}

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