iOS 8应用内跳转到系统设置

iOS 8以后，苹果重新允许从应用内跳转到系统设置，在设置前须判断当前手机系统是否能够跳转到系统设置：
if ([[UIApplicationsharedApplication] canOpenURL:[NSURL URLWithString:UIApplicationOpenSettingsURLString]]) { [[UIApplication sharedApplication] openURL:[NSURL URLWithString:UIApplicationOpenSettingsURLString]]; }