what is the use of an "in-app-purchase" in iphone?

i have already upload my project but i want to upload lite(free) version of my project.but somebody says "in app purchase" is the best way for adding the lite version.but i don't have a idea about in app purchase.i am already shows the app开发者_C百科le documentation and some forums. they were give some ideas but not give a full explanation.

so this situation, i am already add a full version of my project without using in app purchase, so how to add a lite version of my project using in app purchase.

I think you sort of misunderstood your friend's suggestion. What he meant should be,

• Put an iAP (in-app-purchase) module inside your lite version app.
• Make your lite app essentially the same to your full app, but has features that needs to be unlocked by paying a fee.
• Whenever the user feels your lite app is useful and wants to purchase the full version. They can conveniently purchase it right inside your lite app via the iAP module.
• When such a purchase is approved by Apple, you can immediately upgrade your lite app to the full version by unlocking those features.

The value of the in-app purchase is that it allows you to release just one version of your app. Without buying the iAP, it acts as a free app. If the user likes it and wants more features (or, in the case of a game, more levels), they can buy the iAP and unlock that content. This is currently a trend in the iOS App Stores- "freemium" games that entice people due to being free, and hopefully get users "hooked" to pay for the full version.

Advantages over a separate "lite" app:

• Only a single version of the app to update
• Existing user data (save games, whatever) are easily retained
• Even easier purchasing- user doesn't have to leave the app.

Disadvantages:

• Some users find the iAP unlock strategy to be deceptive and prefer the two-app lite/full method.
• In the case of media-heavy apps, especially games, "lite" versions are smaller and faster to download because they don't need all the data of the full version. An iAP "unlockable" app will have all the data of the full version, whether the person ever uses it or not.
• Extra code is needed for the iAP route, though it shouldn't be a problem.

If you decide to go the iAP route, and you've already submitted your full version, you can of course withdraw your binary yourself (provided it isn't on sale yet, of course).