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 
}