{
UIButton *logBtn = [UIButton buttonWithType:UIButtonTypeCustom];
logBtn.frame = CGRectMake(0, kStatusBarHeight, 100, 30);
[logBtn setTitle:@"console" forState:UIControlStateNormal];
logBtn.backgroundColor = UIColor.grayColor;
[logBtn setTitleColor:UIColor.greenColor forState:UIControlStateNormal];
[logBtn addTarget:self action:@selector(logBtnAction) forControlEvents:UIControlEventTouchUpInside];
[self.view addSubview:logBtn];

textView = [[UITextView alloc]initWithFrame:CGRectMake(0,kStatusBarHeight+30, kScreenWidth, kScreenWidth)];
textView.backgroundColor = [UIColor.yellowColor colorWithAlphaComponent:0.25];
[self.view addSubview:textView];
textView.hidden = YES;
[self redirectSTD:STDOUT_FILENO];
[self redirectSTD:STDERR_FILENO];

}
-(void)logBtnAction{
textView.hidden = !textView.hidden;
}

• (void)redirectNotificationHandle:(NSNotification *)nf{ // 通知方法
  NSData *data = [[nf userInfo] objectForKey:NSFileHandleNotificationDataItem];
  NSString *str = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];

  textView.text = [NSString stringWithFormat:@"%@\n\n%@",textView.text, str];// logTextView 就是要将日志输出的视图（UITextView）
  NSRange range;
  range.location = [textView.text length] - 1;
  range.length = 0;
  [textView scrollRangeToVisible:range];
  [[nf object] readInBackgroundAndNotify];
  }

• (void)redirectSTD:(int )fd{
  NSPipe * pipe = [NSPipe pipe] ;// 初始化一个NSPipe 对象
  NSFileHandle *pipeReadHandle = [pipe fileHandleForReading] ;
  dup2([[pipe fileHandleForWriting] fileDescriptor], fd) ;

  [[NSNotificationCenter defaultCenter] addObserver:self
  selector:@selector(redirectNotificationHandle:)
  name:NSFileHandleReadCompletionNotification
  object:pipeReadHandle]; // 注册通知
  [pipeReadHandle readInBackgroundAndNotify];
  }