1：用xib创建tableview的header，footView的时候，不能准确计算出xib的高度。
解决：自己计算出来，先设置带有frame的view给header，footView。再设置xib创建出来添加到view上。

UIView *footerView = [[UIView alloc] initWithFrame:CGRectMake(0, 0, SCREEN_WIDTH , footViewHeight)];
        self.mTableView.tableFooterView = footerView;
        self.visaFootView = [AYVisaFootView gainFootViewFromXib];
        self.visaFootView.frame = CGRectMake(0, 0, self.mTableView.bounds.size.width, footViewHeight);
        [footerView addSubview:self.visaFootView];

2:用reachability判断网络连接状态时，网络连接变化都会监听到。（但是在模拟器上会出现不准确的现象）

+ (NSInteger)getNetStatus:(NetworkChangedBlock)block
{
    __block NSInteger code = 0;
    AFNetworkReachabilityManager *manager = [AFNetworkReachabilityManager sharedManager];
    [manager setReachabilityStatusChangeBlock:^(AFNetworkReachabilityStatus status) {
        //当网络状态发生变化时会调用这个block
        switch (status) {
            case AFNetworkReachabilityStatusReachableViaWiFi:
                code = 1;
                NSLog(@"WiFi");
                break;
            case AFNetworkReachabilityStatusReachableViaWWAN:
                code = 2;
                NSLog(@"手机网络");
                break;
            case AFNetworkReachabilityStatusNotReachable:
                code = -1;
                NSLog(@"没有网络");
                break;
            case AFNetworkReachabilityStatusUnknown:
                code = 0;
                NSLog(@"未知网络");
                break;
                
            default:
                break;
        }
        if (block) {
            block(code);
        }
    }];
    [manager startMonitoring];
    return code;
}

3:AFN的坑，当网络连接正常，服务器端异常。服务器回复正常后，APP端还是请求异常。
这是因为AFN缓存了Url的Response；
解决办法：

    [[NSURLCache sharedURLCache] removeAllCachedResponses];

4:xib进行布局需要动画时,拉出约束,进行约束的更改,用[UIView animateWithDuration:0.2 animations:^{}
进行动画,在block里面调用,父类view的layoutIfNeeded;记住一定是父类的才会起作用.
5:ios 将连接字符串复制到剪贴板

UIPasteboard *pasteboard = [UIPasteboard generalPasteboard];
pasteboard.string = str;//->需要复制的字符串

5:swift 数组的快速排序

let array = [3,5,6,1,0]
let res = array.sorted( by: > )

5:设置滚动位置,不影响输入

- (BOOL)textFieldShouldBeginEditing:(UITextField *)textField
{
    CGPoint point = [_mScrollView convertPoint:textField.bounds.origin fromView:_viewSplitPay];
    CGFloat offsetY = SCREEN_HEIGHT-216.0-64-40-20;
    if (SCREEN_WIDTH == 414) {
        offsetY = offsetY - 10;
    }
    [UIView animateWithDuration:.3 animations:^{
        _mScrollView.contentOffset = CGPointMake(0, point.y-offsetY);
    }];
    return YES;
}