c - Objective-C - SystemSoundID(typedef'd UInt32)是否自动分配为 0？

Question

- (void)playAlarmSound:(NSTimer *)theTimer {
    static SystemSoundID soundID/* = 0 */; // ?
    if (!soundID) {
        soundID = [Utilities createSystemSoundIDFromFile:@"beep" ofType:@"caf"];
    }
    ...
}

SystemSoundID(是一个UInt32)是否自动赋值0？还是我应该明确分配它？我必须这样做并测试它是否未被 Utilities 方法初始化，因为如果我只是执行 static SystemSoundID soundID = [Utilities createSystemSoundIDFromFile:@"beep"ofType:@ 它不会编译“咖啡馆”];。起初我尝试将它分配给 NULL，但后来我意识到它不是一个指针，所以不管怎样，我应该在那里有 = 0 还是它是多余的？

Answer 1

这道题不涉及任何objective-c特性，所以答案在c标准中。

C99，第 6.7.8 节，第 10 段:

If an object that has static storage duration is not initialized explicitly, then:

...

— if it has arithmetic type, it is initialized to (positive or unsigned) zero;

UInt32(它本身就是 uint32_t)是一种算术类型。因此，初始化为零。