我可以安全地从iOS 7调用iOS 8选择器吗？

Question

我正在为iOS 8实现新的核心位置权限，但我想使用Xcode 5.1.1和iOS 7.1 SDK进行编译和发布。

具体来说，我想调用方法＆＃34; requestWhenInUseAuthorization＆＃34;在CLLocationManager上，仅在iOS 8中可用。

这样做有什么风险？这是一个好习惯吗？我可以忽略“未声明的选择器”吗？的警告？

// Warning: Undeclared Selector
SEL requestWhenInUse = @selector(requestWhenInUseAuthorization); 
if( [self.sharedLocationManager respondsToSelector:requestWhenInUse] )
{
    // Warning: May cause leak because selector is unknown
    [self.sharedLocationManager performSelector:requestWhenInUse];
}
[self.sharedLocationManager startUpdatingLocation];

Answer 1

你的代码很好。要取消警告，请添加

@interface CLLocationManager (iOS8Method)

- (void)requestWhenInUseAuthorization;

@end

然后你可以调用方法

if( [self.sharedLocationManager respondsToSelector:@selector(requestWhenInUseAuthorization)] )
{
    [self.sharedLocationManager requestWhenInUseAuthorization];
}

还阅读了这个问题：performSelector may cause a leak because its selector is unknown