instancesrespondToSelector 是什么意思。与 respondsToSelector 有什么区别?
2013-12-23 17:06
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iOS开发中如何判断一个类是否支持某属性和方法以及如何判断
instancesRespondToSelector是指类的实例们是否能响应某一个方法(类操作),respondsToSelector是指类是否能响应某一方法(对象)
举例:
instancesRespondToSelector:[AVPlayerItem instancesRespondToSelector:@selector(duration)]
;(建议使用这种方式)
使用这种方式也可以判断IOS系统的版本是否支持某个方法或者属性
举例:
if ([AVPlayerItem instancesRespondToSelector:@selector(duration)]) {
// On iOS 4.3 we get here...
cTime = _avPlayer.currentItem.duration;
}
else
{
//On IOS 4.2 we get here...
cTime = _avPlayer.currentItem.asset.duration;
}
...
}
respondsToSelector:(同样可以达到效果)
UIDevice* device = [UIDevice currentDevice];
if ([device respondsToSelector:@selector(isMultitaskingSupported)]) {
_multitaskingSupported = device.multitaskingSupported;
}
instancesRespondToSelector是指类的实例们是否能响应某一个方法(类操作),respondsToSelector是指类是否能响应某一方法(对象)
举例:
instancesRespondToSelector:[AVPlayerItem instancesRespondToSelector:@selector(duration)]
;(建议使用这种方式)
使用这种方式也可以判断IOS系统的版本是否支持某个方法或者属性
举例:
if ([AVPlayerItem instancesRespondToSelector:@selector(duration)]) {
// On iOS 4.3 we get here...
cTime = _avPlayer.currentItem.duration;
}
else
{
//On IOS 4.2 we get here...
cTime = _avPlayer.currentItem.asset.duration;
}
...
}
respondsToSelector:(同样可以达到效果)
UIDevice* device = [UIDevice currentDevice];
if ([device respondsToSelector:@selector(isMultitaskingSupported)]) {
_multitaskingSupported = device.multitaskingSupported;
}
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