保存日志到手机：
1、将下面的代码加到Appdelegate里，在didFinshLunch中调用
2、手机连接到Mac，在Xcode中Window—》Device —》选中当前设备和app 在下面选择DownLoadContainer

- (void)redirectNSLogToDocumentFolder
{
    //如果已经连接Xcode调试则不输出到文件
//    if(isatty(STDOUT_FILENO)) {
//        return;
//    }
    
    UIDevice *device = [UIDevice currentDevice];
    if([[device model] hasSuffix:@"Simulator"]){ //在模拟器不保存到文件中
        return;
    }
    
    //将NSlog打印信息保存到Document目录下的Log文件夹下
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *logDirectory = [[paths objectAtIndex:0] stringByAppendingPathComponent:@"Log"];
    
    NSFileManager *fileManager = [NSFileManager defaultManager];
    BOOL fileExists = [fileManager fileExistsAtPath:logDirectory];
    if (!fileExists) {
        [fileManager createDirectoryAtPath:logDirectory  withIntermediateDirectories:YES attributes:nil error:nil];
    }
    
    NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
    [formatter setLocale:[[NSLocale alloc] initWithLocaleIdentifier:@"zh_CN"]];
    [formatter setDateFormat:@"yyyy-MM-dd HH:mm:ss"]; //每次启动后都保存一个新的日志文件中
    NSString *dateStr = [formatter stringFromDate:[NSDate date]];
    NSString *logFilePath = [logDirectory stringByAppendingFormat:@"/%@.log",dateStr];
    
    // 将log输入到文件
    freopen([logFilePath cStringUsingEncoding:NSASCIIStringEncoding], "a+", stdout);
    freopen([logFilePath cStringUsingEncoding:NSASCIIStringEncoding], "a+", stderr);
    
    //未捕获的Objective-C异常日志
//    NSSetUncaughtExceptionHandler (&UncaughtExceptionHandler);
}