同一行上的赋值和比较运算符

Question

我试图弄清楚这是做什么或者什么是简写？

_var1 = _var2 == nil;

我一直在测试

_thing1 = 1;
_thing2 = 2;
_thing3 = 3;

NSLog(@"thing1 before %li",(long)_thing1);
NSLog(@"thing2 before %li",(long)_thing2);
NSLog(@"thing2 before %li",(long)_thing3);

_thing1 = _thing1 == _thing3;

NSLog(@"thing1 after %li",(long)_thing1);
NSLog(@"thing2 after %li",(long)_thing2);
NSLog(@"thing3 after %li",(long)_thing3);

我只得到_或1的1或0。这是否意味着它只是检查平等？

Answer 1

等于

int temp = _ting1 == ting3;
_thing1 = temp;

所以_thing1如果相等则为1（是），否则为0（否）

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另一种写_var1 = _var2 == nil;的方式是_var1 = !_var2;有些人认为第二种方式更具可读性（包括我），有些人更喜欢第一种方式。

Answer 2

您只是指定不等式的值。 _thing1等于if _thing1等于_thing3。

例如：

int aa = 1;
int bb = 2;
int cc = 3;
NSLog(@"%d", aa); // 1 (the value that was set for aa)
aa = aa == b;
NSLog(@"%d", aa); // 0 - which means false (1 means true)