为什么我的代码与我一起初始化 NSInteger？
我有一个接口
@interface MyInterface
{
NSInteger _count;
}
@end
然后在我的实现中我只是使用 is as
if (_count==0)
{
//do somthing
}
_count++;
并且它可以工作，即第一次执行时该值实际上是 0，即使我从未将其初始化为零。
是因为NSInteger的默认值是0吗？
Possible Duplicate:
(Objective-)C ints always initialized to 0?
I have an interface
@interface MyInterface
{
NSInteger _count;
}
@end
Then in my implementation I am just using is as
if (_count==0)
{
//do somthing
}
_count++;
And it works i.e. the first time around when this is executed the value is in fact 0 even though I never initialized it to be zero.
Is it because the default value of NSInteger is 0?
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假设您打算编写
==而不是=，答案是 Objective-C 类的所有实例变量 (ivars) 都会初始化为 0 或nil当对象被创建时。请参阅问题（Objective-）C 整数始终初始化为 0？ 。如果您实际上使用单个
=编写了if (_count = 0)，那么这并没有达到您的预期 - 它会将 0 分配给_count，然后测试它是否非零（表达式if (x)测试x是否非零）。由于您刚刚为其分配了 0，因此它不是非零，因此测试总是会失败。Assuming you meant to write
==instead of=, the answer is that all of the instance variables (ivars) of an Objective-C class get initialized to 0 ornilwhen the object gets created. See the question (Objective-)C ints always initialized to 0?.If you actually wrote
if (_count = 0)with a single=, then that's not doing what you expected -- it's assigning 0 to_count, and then testing if it's non-zero (the expressionif (x)tests ifxis non-zero). Since you just assigned 0 to it, it's not non-zero, so the test will always fail.更改 if 语句以
记住双等于是比较，单等于是赋值
change your if statement to
remember double equals is comparison, single equals is assignment
您使用
此功能会将值
0设置为变量_count，如果此操作成功，则会执行{}之间的代码来测试变量的值使用比较运算符
==you are using
this will set value
0to variable_count, and if this action success, code between{}is executedto test value of variable use comparison operator
==