iOS swap 操作的三种写法

要点：传递地址，操作指针

方法一：

- (void)viewDidLoad {
    [super viewDidLoad];
    
    int a = 10;
    int b = 20;
    [self swapA:&a B:&b];
    NSLog(@"外部：a:%d b:%d",a,b);
    // Do any additional setup after loading the view, typically from a nib.
}

-(void)swapA:(int *)a B:(int *)b{
    int temp = *a;
    *a = *b;
    *b = temp;
    NSLog(@"内部：a:%d b:%d",*a,*b);
}

内部：a:20 b:10
外部：a:20 b:10

方法二：调用方法和控制台打印同方法一

-(void)swapA:(int *)a B:(int *)b{
    *b = *a ^ *b;
    *a = *a ^ *b;
    *b = *a ^ *b;
    NSLog(@"内部：a:%d b:%d",*a,*b);
}

方法三：调用方法和控制台打印同方法一

-(void)swapA:(int *)a B:(int *)b{
    *a = *a + *b;
    *b = *a - *b;
    *a = *a - *b;
    NSLog(@"内部：a:%d b:%d",*a,*b);
}

错误案例：

- (void)viewDidLoad {
    [super viewDidLoad];
    
    int a = 10;
    int b = 20;
    [self swapA:&a B:&b];
    NSLog(@"外部：a:%d b:%d",a,b);
    // Do any additional setup after loading the view, typically from a nib.
}

-(void)swapA:(int *)a B:(int *)b{
    int *temp = a;
    a = b;
    b = temp;
    NSLog(@"内部：a:%d b:%d",*a,*b);
}

内部：a:20 b:10
外部：a:10 b:20

- (void)viewDidLoad {
    [super viewDidLoad];
    
    int a = 10;
    int b = 20;
    [self swapA:a B:b];
    NSLog(@"外部：a:%d b:%d",a,b);
    // Do any additional setup after loading the view, typically from a nib.
}

-(void)swapA:(int)a B:(int)b{
    int temp = a;
    a = b;
    b = temp;
    NSLog(@"内部：a:%d b:%d",a,b);
}

内部：a:20 b:10
外部：a:10 b:20