view - My IAP isn't working. Bugs at func Paymentqueue

Question

When I click on either of my IAPS, a message appears saying the IAP was already purchased (which is not the case) and will be restored for free, then nothing happens, the IAP doesn't execute.

Here is what I get in my console:

No Value.
IAP is enabled, loading...

true
Product Request
Product Added
IAP id
Remove Ads
Removes ads from the app.
2
Buy: IAP id
Add Payment
nil
default: Error

Here is my code:

GameViewController.Swift

import UIKit
import StoreKit


class GameViewController: UIViewController, ADBannerViewDelegate, SKProductsRequestDelegate, SKPaymentTransactionObserver, GKGameCenterControllerDelegate,GADBannerViewDelegate{


    @IBOutlet var outRemoveAds: UIButton!
    @IBOutlet var outRestorePurchases: UIButton!


    override func viewDidLoad() {
        super.viewDidLoad()
    }

    override func viewWillAppear(animated: Bool) {
        super.viewWillAppear(animated)

        if NSUserDefaults.standardUserDefaults().objectForKey("val") != nil {
            print("Has a value.")
            banner.removeFromSuperview()
            bannerGoogle.removeFromSuperview()
            outRemoveAds.removeFromSuperview()
            outRestorePurchases.removeFromSuperview()
            removeInterFrom = 1
        }
        else {
            print("No Value.")
        }

        if(SKPaymentQueue.canMakePayments()){
            print("IAP is enabled, loading...")
            let productID:NSSet = NSSet(objects:"IAP id")
            let request: SKProductsRequest = SKProductsRequest(productIdentifiers: productID as! Set<String>)
            request.delegate = self
            request.start()
        }
        else{
            print("Please enable IAPS")

        }

    }


    //IAP Ads

    @IBAction func removeAds(sender: UIButton) {
        for product in list{
            let prodID = product.productIdentifier
            if (prodID == "IAP id"){
                p = product
                buyProduct()
                break
            }
        }
    }
    @IBAction func restorePurchases(sender: UIButton) {
        SKPaymentQueue.defaultQueue().addTransactionObserver(self)
        SKPaymentQueue.defaultQueue().restoreCompletedTransactions()
    }


    //IAP Functions

    var list = [SKProduct]()
    var p = SKProduct()

    func removeAds(){
        banner.removeFromSuperview()
        bannerGoogle.removeFromSuperview()
        outRemoveAds.removeFromSuperview()
        outRestorePurchases.removeFromSuperview()
        let theValue = 10
        NSUserDefaults.standardUserDefaults().setObject(theValue, forKey: "val")
        NSUserDefaults.standardUserDefaults().synchronize()
    }

    func buyProduct(){
        print("Buy: "+p.productIdentifier)
        let pay = SKPayment (product: p)
        SKPaymentQueue.defaultQueue().addTransactionObserver(self)
        SKPaymentQueue.defaultQueue().addPayment(pay as SKPayment)
    }

    func productsRequest(request: SKProductsRequest, didReceiveResponse response: SKProductsResponse) {
        print("Product Request")
        let myProduct = response.products

        for product in myProduct{
            print("Product Added")
            print(product.productIdentifier)
            print(product.localizedTitle)
            print(product.localizedDescription)
            print(product.price)

            list.append(product as SKProduct)
        }
    }

    func paymentQueue(queue: SKPaymentQueue, updatedTransactions transactions: [SKPaymentTransaction]) {
        print("Add Payment")

        for transaction:AnyObject in transactions{
            let trans = transaction as! SKPaymentTransaction
            print(trans.error)
            switch trans.transactionState{
            case .Purchased:
                print("IAP unlocked")
                print(p.productIdentifier)

                let prodID = p.productIdentifier as String
                switch prodID{
                case "IAP id":
                    print("Remove Ads")
                    removeAds()
                default:
                    print("IAP not setup")
                }
                queue.finishTransaction(trans)
                break
            case .Failed:
                print ("Buy error")
                queue.finishTransaction(trans)
                break
            default:
                print("default: Error")
                break
            }
        }
    }

    func paymentQueueRestoreCompletedTransactionsFinished(queue: SKPaymentQueue) {
        print("Purchases Restored")

        _ = []
        for transaction in queue.transactions {
            let t: SKPaymentTransaction = transaction as SKPaymentTransaction

            let prodID = t.payment.productIdentifier as String
            switch prodID{
            case "IAP id":
                print("Remove Ads")
                removeAds()
            default:
                print("IAP not setup")
            }


        }
    }
    func finishTransaction(trans:SKPaymentTransaction){
        print("Finshed Transaction")
    }

    func paymentQueue(queue: SKPaymentQueue, removedTransactions transactions: [SKPaymentTransaction]) {
        print("Remove Transaction")
    }
}

MenuViewController.swift

import UIKit
import StoreKit
import Social




class MenuViewController: UIViewController, SKProductsRequestDelegate,SKPaymentTransactionObserver {

    @IBOutlet var outRestart: UIButton!
    @IBOutlet var outBuy: UIButton!



    override func viewDidLoad() {
        super.viewDidLoad()

    }

    override func viewWillAppear(animated: Bool) {
        super.viewWillAppear(animated)


        if(SKPaymentQueue.canMakePayments()){
            print("IAP is enabled, loading...")
            let productID:NSSet = NSSet(objects:"IAP id")
            let request: SKProductsRequest = SKProductsRequest(productIdentifiers: productID as! Set<String>)
            request.delegate = self
            request.start()
        }
        else{
            print("Please enable IAPS")

        }

    }


    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }

    @IBAction func buy(sender: UIButton) {
        for product in list{
            let prodID = product.productIdentifier
            if (prodID == "IAP id"){
                p = product
                buyProduct()
                break
            }
        }

    }

    //IAP Functions

    var list = [SKProduct]()
    var p = SKProduct()

    func keepOn(){
        buyornot = 1
        Back()
    }

    func buyProduct(){
        print("Buy: "+p.productIdentifier)
        let pay = SKPayment (product: p)
        SKPaymentQueue.defaultQueue().addTransactionObserver(self)
        SKPaymentQueue.defaultQueue().addPayment(pay as SKPayment)
    }

    func productsRequest(request: SKProductsRequest, didReceiveResponse response: SKProductsResponse) {
        print("Product Request")
        let myProduct = response.products

        for product in myProduct{
            print("Product Added")
            print(product.productIdentifier)
            print(product.localizedTitle)
            print(product.localizedDescription)
            print(product.price)

            list.append(product as SKProduct)
        }
    }

    func paymentQueue(queue: SKPaymentQueue, updatedTransactions transactions: [SKPaymentTransaction]) {
        print("Add Payment")

        for transaction:AnyObject in transactions{
            let trans = transaction as! SKPaymentTransaction
            print(trans.error)
            switch trans.transactionState{
            case .Purchased:
                print("IAP unlocked")
                print(p.productIdentifier)

                let prodID = p.productIdentifier as String
                switch prodID{
                case "IAP id":
                    print("Keep on")
                    keepOn()
                default:
                    print("IAP not setup")
                }
                queue.finishTransaction(trans)
                break
            case .Failed:
                print ("Buy error")
                queue.finishTransaction(trans)
                break
            default:
                print("default: Error")
                break
            }
        }
    }

    func finishTransaction(trans:SKPaymentTransaction){
        print("Finshed Transaction")
    }

    func paymentQueue(queue: SKPaymentQueue, removedTransactions transactions: [SKPaymentTransaction]) {
        print("Remove Transaction")
    }

Answer 1

I found the solution !

Delete

SKPaymentQueue.defaultQueue().addTransactionObserver(self) 

everywhere you have it and put it once (ONLY ONCE) in a place where it will be executed each time your app boots up ( I put it in viewDidLoad()).

This will check for all unfinished transactions and terminate them once the app has loaded, thus removing any possible errors before your users triggers an IAP.

(If this answer, or this question helped you, don't forget to upvote ;))

P.S.: Also, this wasn't my issue, but make sure to finishTransaction() for each PurchaseState like here:

func paymentQueue(queue: SKPaymentQueue, updatedTransactions transactions: [SKPaymentTransaction]) {
        print("Add Payment")

        for transaction:AnyObject in transactions{
            let trans = transaction as! SKPaymentTransaction
            print(trans.error)
            switch trans.transactionState{
            case .Purchased:
                print("IAP unlocked")
                print(p.productIdentifier)

                let prodID = p.productIdentifier as String
                switch prodID{
                case "IAP id":
                    print("Keep on")
                    keepOn()
                default:
                    print("IAP not setup")
                }
                queue.finishTransaction(trans)
                break
            case .Failed:
                print ("Buy error")
                queue.finishTransaction(trans)
                break
            default:
                print("default: Error")
                break
            }
        }
    }

Never forget this:

 queue.finishTransaction(trans)