Can we install iPhone SDK 4 in iPhone OS 3

Question

Can i install a iPhone4 SDK, where my Mac Book has only iPhone OS3? If it is possible will i get all the features of iPhone OS4?

Answer 1

yes, you can update it. but do this only of you need features of new iOS 4 (multitask and so on). if you are don't i guess u colud stay on iOS 3

Answer 2

所有新的iOS4 API都包含在iPhone SDK 4中，因此只需下载并开始开发即可。

Answer 3

The installation of iOS SDK 4.0 removes all SDK's before 3.2. However, you're still able to develop for your 3.0 devices.

• set Base SDK to 4.0
• set Deployment Target (Target -> Info -> Build : "iPhone OS Deployment Target" ) "to iPhone OS 3.0"

be aware of the fact that if you develop your app for 3.0, the use of API's oder Methods within API's only available from 4.0 onwards will crash your app.

the use of the "respondsToSelector" Method will let you know if a method is available on the current device that is executing your code. This enables you to make use of the new API's if your app runs on a 4.0 device whilst maintaining "backwards"-compatibility for 3.0 (or whatever OS Version you set as Deployment Target"

if([[UIApplication sharedApplication] respondsToSelector:@selector(setStatusBarHidden: withAnimation:)])