iOS In app purchase

An in-app purchase (or IAP) allows developers to charge users for specific functionality or content while using an app. Implementing IAPs is particularly compelling for several reasons:

When creating app ID, need to notice that Scroll down to the App Services section. Notice that In-App Purchase and GameCenter are enabled by default. Click Continue and then Register and Done. Next, you’ll create a matching app in App Store Connect.

Below two things are mandatory before enabling IAP in the app


    Make sure you have accepted the latest Apple Development Program License Agreement on developer.apple.com.
    Make sure you have accepted the latest Paid Applications agreement in the Agreements, Tax, and Billing section in App Store Connect.


If you see a section entitled Request Contracts containing a row for Paid Applications, then click the Request button. Fill out all the necessary information and submit it. It may take some time for your request to be approved. Sit tight!

Otherwise, if you see Paid Applications listed under Contracts In Effect, then it looks like you’ve already done this step! Nice job!

Apple can take days to approve these IAP-related agreements after you submit them. During this time, you won’t be able to display IAP products in your apps even if you implement everything correctly in code. This is a common source of frustration for folks implementing In-App Purchases for the first time. Hang in there!

Creating In-App Purchase Products

When offering IAPs you must first add an entry for each individual purchase within App Store Connect. If you’ve ever listed an app for sale in the store, it’s a similar process and includes things like choosing a pricing tier for the purchase. When the user makes a purchase, the App Store handles the complex process of charging the user and reply with data about such operation.

There are a whole bunch of different types of IAP you can add:

Below are different types of IAPs

 Consumable: These can be bought more than once and can be used up. These are a good fit for extra lives, in-game currency, temporary power-ups, and the like.
Non-Consumable: Something that you buy once, and expect to have permanently such as extra levels and unlockable content. The RazeFace illustrations from this tutorial fall into this category.

Non-Renewing Subscription: Content that’s available for a fixed period of time.

Auto-Renewing Subscription: A repeating subscription such as a monthly

We can only offer In-App Purchases for digital items, and not for physical goods or services.


Below are the few things to be entered for making an IAP product

Next, fill out the details for the IAP as follows:

    Reference Name: A nickname identifying the IAP within iTunes Connect. This name does not appear anywhere in the app. The title of the RazeFace you’ll be unlocking with this purchase is Swift Shopping, so enter that here.

    Product ID: This is a unique string identifying the IAP. Usually it’s best to start with the Bundle ID and then append a unique name specific to this purchasable
item. For this tutorial, make sure you append swiftshopping, as this will be used later within the app to look up the RazeFace to unlock. For example, you can use: com.theNameYouPickedEarlier.razefaces.swiftshopping.

    Cleared for Sale: Enables or disables the sale of the IAP. You want to enable it!
    Price Tier: The cost of the IAP. Choose Tier 1.


There’s one more step required before you can delve into some code. When testing in-app purchases in a development build of an app, Apple provides a test environment which allows you to “purchase” your IAP products without creating financial transactions.

These special test purchases can only be made by a special “Sandbox Tester” user account in App Store Connect. You’re almost at the code, I promise!



References:
https://www.raywenderlich.com/5456-in-app-purchase-tutorial-getting-started