这个问题找了大半天实在是解决不了就问了别的朋友，最后败在了一段代码上，我都抓狂了，要杀人
坑在了log输出日志文件
- (void)redirectNSlogToDocumentFolder
{
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentDirectory = [paths objectAtIndex:0];
NSString *fileName = [NSString stringWithFormat:@"iOSLive.log"];// 注意不是NSData!
NSString *logFilePath = [documentDirectory stringByAppendingPathComponent:fileName];
// 先删除已经存在的文件
NSFileManager *defaultManager = [NSFileManager defaultManager];
[defaultManager removeItemAtPath:logFilePath error:nil];
// 将log输入到文件
freopen([logFilePath cStringUsingEncoding:NSASCIIStringEncoding], "a+", stdout);
freopen([logFilePath cStringUsingEncoding:NSASCIIStringEncoding], "a+", stderr);
}
