更新时间:2022-06-13 02:32:30
没有实际区别提供你使用 BOOL
变量作为布尔值.C 会根据布尔表达式的计算结果是否为 0 来处理布尔表达式.所以:
There is no practical difference provided you use BOOL
variables as booleans. C processes boolean expressions based on whether they evaluate to 0 or not 0. So:
if(someVar ) { ... }
if(!someVar) { ... }
意思相同
if(someVar!=0) { ... }
if(someVar==0) { ... }
这就是为什么您可以将任何原始类型或表达式评估为布尔测试(包括,例如指针).请注意,您应该做前者,而不是后者.
which is why you can evaluate any primitive type or expression as a boolean test (including, e.g. pointers). Note that you should do the former, not the latter.
请注意,如果您将钝值分配给所谓的 BOOL
变量并测试特定值,则存在差异,因此始终将它们用作布尔值并仅从它们的 #define
值中分配它们.
Note that there is a difference if you assign obtuse values to a so-called BOOL
variable and test for specific values, so always use them as booleans and only assign them from their #define
values.
重要的是,永远不要使用字符比较来测试布尔值——这不仅是有风险的,因为 someVar
可以被分配一个不是 YES 的非零值,但在我看来更重要的是,它失败了正确表达意图:
Importantly, never test booleans using a character comparison -- it's not only risky because someVar
could be assigned a non-zero value which is not YES, but, in my opinion more importantly, it fails to express the intent correctly:
if(someVar==YES) { ... } // don't do this!
if(someVar==NO ) { ... } // don't do this either!
换句话说,按照预期和记录使用的构造来使用,这样您就不会在 C 语言中受到伤害.
In other words, use constructs as they are intended and documented to be used and you'll spare yourself from a world of hurt in C.