向大佬学习

 a = ( a + b ) -  ( b = a );

或者使用异或运算

a = a ^ b; b = a ^ b; a = a ^ b;

a^=b^=a^=b;

代码测试成功

   int a = 123,  b = 678;
     //交换值
    a = ( a + b ) -  ( b = a );
    NSLog(@"a=%d, b = %d",a,b);
测试结果：
2019-07-24 17:56:09.002894+0800 test[42881:5910344] a=678, b = 123

给view同时加上圆角和阴影

使用 maskedCorners，CACornerMask