I want to implement application in which I want to purchase other application from my application. Can you provide me guidance about that or any sample code for that?
I have made one application and suppose right now is in the apple store. Now every month I want collect payment from the client for this application. Then how to make this type of appliation. Is it possible? If yes then please advise me or give me some idea or ant samele code.
I think you want the "In App Purchasing Guide". It tells you how to set up transactions within your application.
You can as of iPhone OS 3.0 upgrade an applications from within an earlier version of that application but you cannot download and install other, completely separate applications. Doing so would require breaking the app sandbox and would raise major security and reliability concerns.
Remember that the iPhone has a unique business model. You can't think of it as just a small desktop computer.