IOS判断版本

1. iOS版本确认

- (void)viewDidLoad {
[super viewDidLoad];

if ([[[UIDevice currentDevice] systemVersion] floatValue] >= 4.0) {
bannerView = [[ADBannerView alloc] init];
bannerView.delegate = self;
[self.view addSubview:bannerView];
}

2. 新类是否存在

Class clazz = NSClassFromString(@"ADBannerView");if (clazz) {bannerView = [[ADBannerView alloc] init];bannerView.delegate = self;[self.view addSubview:bannerView];}

3. 新接口是否存在

if (UIGraphicsBeginImageContextWithOptions != NULL) {bannerView = [[ADBannerView alloc] init];bannerView.delegate = self;[self.view addSubview:bannerView];}