Purchase Flow

Key Concepts

• Always call initConnection() before any IAP operations
• Listen to purchaseUpdatedListener and purchaseErrorListener for purchase results
• Always call finishTransaction() after processing a purchase
• Verify purchases server-side in production

Initialize

kmpIapInstance.initConnection()

Fetch Products

val products = kmpIapInstance.fetchProducts {
    skus = listOf("coins_100", "premium_upgrade")
    type = ProductQueryType.InApp
}

Listen for Purchases

// Success
kmpIapInstance.purchaseUpdatedListener.collect { purchase ->
    // 1. Verify on server
    // 2. Deliver content
    // 3. Finish transaction
    kmpIapInstance.finishTransaction(
        purchase = purchase.toPurchaseInput(),
        isConsumable = true
    )
}

// Errors
kmpIapInstance.purchaseErrorListener.collect { error ->
    when (error.code) {
        ErrorCode.UserCancelled -> { /* Silent */ }
        ErrorCode.AlreadyOwned -> { /* Suggest restore */ }
        else -> { /* Show error */ }
    }
}

Request Purchase

kmpIapInstance.requestPurchase {
    ios {
        sku = "coins_100"
        // Optional: Attribution tracking (v1.3.7+)
        // advancedCommerceData = "campaign_id"
    }
    google { skus = listOf("coins_100") }  // Recommended (v1.3.15+)
}

Restore Purchases

val purchases = kmpIapInstance.getAvailablePurchases()
purchases.forEach { purchase ->
    // Re-deliver non-consumables
}

Cleanup

kmpIapInstance.endConnection()

IAPKit Server Verification

For production apps, always verify purchases server-side. IAPKit provides a simple unified API for both iOS and Android verification.

Setup

1. Get your API key from iapkit.com
2. Configure environment variables:

Android (.env or local.properties):

IAPKIT_API_KEY=your_api_key_here

iOS (Secrets.xcconfig):

IAPKIT_API_KEY = your_api_key_here

How It Works

// In your purchase listener
kmpIapInstance.purchaseUpdatedListener.collect { purchase ->
    val purchaseToken = purchase.purchaseToken
    if (purchaseToken.isNullOrEmpty()) {
        showError("No purchase token available")
        return@collect
    }

    try {
        val result = kmpIapInstance.verifyPurchaseWithProvider(
            VerifyPurchaseWithProviderProps(
                provider = PurchaseVerificationProvider.Iapkit,
                iapkit = RequestVerifyPurchaseWithIapkitProps(
                    apiKey = AppConfig.iapkitApiKey,
                    apple = RequestVerifyPurchaseWithIapkitAppleProps(jws = purchaseToken),
                    google = RequestVerifyPurchaseWithIapkitGoogleProps(purchaseToken = purchaseToken)
                )
            )
        )

        if (result.iapkit?.isValid == true) {
            // Grant entitlement to user
            deliverProduct(purchase.productId)

            // Finish the transaction
            kmpIapInstance.finishTransaction(
                purchase = purchase.toPurchaseInput(),
                isConsumable = isConsumable(purchase.productId)
            )
        } else {
            showError("Purchase verification failed: ${result.iapkit?.state}")
        }
    } catch (e: Exception) {
        showError("Verification error: ${e.message}")
    }
}

Verification Response

{
  "isValid": true,
  "state": "ENTITLED",
  "store": "APPLE"
}

// Access in code
val isValid = result.iapkit?.isValid     // true
val state = result.iapkit?.state         // IapkitPurchaseState.Entitled
val store = result.iapkit?.store         // IapStore.Apple or IapStore.Google

Verification Methods

Method	Use Case	Security
None	Development only	None
Local	Basic validation	Low
IAPKit	Production apps	High

Benefits of IAPKit

• Unified API for iOS and Android
• Real-time fraud detection
• Subscription status tracking
• Sandbox/Production environment detection
• No backend infrastructure needed

For more details, visit the IAPKit Documentation.

IAPKit Purchase States

State	Description
Entitled	Valid access
Expired	Subscription expired
Canceled	Purchase canceled
Consumed	Consumable used
Inauthentic	Fraudulent

Next Steps

• Subscription Flow - Recurring payments
• Error Codes - Handle all error types