ios - SwiftyStoreKit - when to perform receipt validation

Question

I'm using SwiftyStoreKit to perform subscriptions:

private func subscribeUser(withId subscriptionId: String) {
    SwiftyStoreKit.purchaseProduct(subscriptionId, atomically: false) { result in
        switch result {
        case .success(let product):
            
            if product.needsFinishTransaction {
                SwiftyStoreKit.finishTransaction(product.transaction)
            }
            
            // Get the receipt
            SwiftyStoreKit.fetchReceipt(forceRefresh: true) { result in
                switch result {
                case .success(let receiptData):
                    // Encrypt the receipt
                    let encryptedReceipt = receiptData.base64EncodedString(options: [])
                    
                    // Set up verification url
                    let url = "https://myUrl/verifyReceipt"
                    
                    // Send receipt to server
                    APIConnect.verifyReceipt(
                        url: url,
                        params: ["receipt" : encryptedReceipt],
                        completion: self.processSubscription)
                    
                    
                case .error(let error):
                    print("SUBSCRIPTIONPAYMENTVC | subscribeUser | Fetch receipt failed: (error)")
                }
            }
            
        case .error(let error):
            switch error.code {
                // alert user accordingly
            }
        }
    }
}

After the receipt is sent to our server and verified, the response is handled:

func processSubscription(receiptJSON: JSON) {
    print("SUBSCRIPTIONPAYMENTVC | verifySubscription | Done Verifying Subscription")
    
    // Check response
    if receiptJSON["status"] > 0 {
        
        // alert user accordingly
        
    } else {
    
        // Get data from receipt
        let lastReceiptIndex = receiptJSON["latest_receipt_info"].arrayValue.count - 1
        
        // Set up varibles
        productId = receiptJSON["latest_receipt_info"][lastReceiptIndex]["product_id"].stringValue
        originalTransactionId = receiptJSON["latest_receipt_info"][lastReceiptIndex]["original_transaction_id"].stringValue
        startDate = receiptJSON["latest_receipt_info"][lastReceiptIndex]["original_purchase_date_ms"].stringValue
        endDate = receiptJSON["latest_receipt_info"][lastReceiptIndex]["expires_date_ms"].stringValue
        latestReceipt = receiptJSON["latest_receipt"].stringValue
        
        // Add user to database
        addUserToDB()
        
    }
}

However, wouldn't the user have already been charged even though processSubscription could receive a status > 0? Am I calling receipt verification at a wrong time? Where exactly does the purchase take place and how can it be blocked by the verification?

question from:https://stackoverflow.com/questions/65849245/swiftystorekit-when-to-perform-receipt-validation

Answer 1

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