获取iphone系统版本号

    NSLog([[UIDevice currentDevice] name]); // Name of the phone as named by user

    NSLog([[UIDevice currentDevice] uniqueIdentifier]); // A GUID like string

    NSLog([[UIDevice currentDevice] systemName]); // "iPhone OS"

    NSLog([[UIDevice currentDevice] systemVersion]); // "2.2.1"

    NSLog([[UIDevice currentDevice] model]); // "iPhone" on both devices

    NSLog([[UIDevice currentDevice] localizedModel]); // "iPhone" on both devices

    float version = [[[UIDevice currentDevice] systemVersion] floatValue];

    if (version >= 4.0)

    {

        // iPhone 4.0 code here 

    }