iphone - iPod : What does NS_NONATOMIC_IPHONEONLY mean? 在 iPod Touch 上使用此类属性是否安全？

Question

在属性部分下的CLLocation类引用内，它表示坐标:

coordinate
The geographical coordinate information. (read-only)

@property(readonly, NS_NONATOMIC_IPHONEONLY) CLLocationCoordinate2D coordinate
Discussion
When running in the simulator, Core Location assigns a fixed set of coordinate values to this property. You must run your application on an iOS-based device to get real location values.

Special Considerations
In iOS, this property is declared as nonatomic. In Mac OS X, it is declared as atomic.

我只是好奇这意味着什么:@property(readonly, NS_NONATOMIC_IPHONEONLY)。特别是 NS_NONATOMIC_IPHONEONLY 部分。在我看来，我可以通过 iPod touch 访问此内容。

我错过了什么吗？从 iPod touch 使用此功能安全吗？

Answer 1

CoreLocation 在 Mac OS X 和 iOS(née iPhone OS)之间共享。

这里，NS_NONATOMIC_IPHONEONLY仅表示该属性在 iOS 上是非原子的，在 Mac OS X 上是原子的。这里的 iPhone 仅指 iOS，而不是 iPhone 与 iPod touch。

它在 TargetConditionals.h 中定义如下。

// Marks APIs whose iPhone versions are nonatomic, that is cannot be set/get from multiple threads safely without additional synchronization
#if !defined(NS_NONATOMIC_IPHONEONLY)
    #if TARGET_OS_IPHONE
    #define NS_NONATOMIC_IPHONEONLY nonatomic
    #else
    #define NS_NONATOMIC_IPHONEONLY
    #endif
#endif