Swift Method Chaining with Success & Failure - ios

Question

I am trying to implement method chaining for success and failure calls in my code but I seem to be having trouble getting the onSuccess methods to actually be called.
A view controller calls the getProduct(_:) function.
getProduct(_:) makes an API call and then calls storeProduct(_:) with the retrieved json
storeProduct(_:) calls fetchProduct(_:)
fetchProduct(_:) calls doSuccess(_:) but this never gets back into the onSuccess of the previous calls.
Some Code Snippets
BSProductChainable.swift
import Foundation
class BSProductChainable<SuccessParams, FailureParams> {
var successClosure: ((SuccessParams) -> ())? = nil
var failureClosure: ((FailureParams) -> ())? = nil
func onSuccess(closure: (SuccessParams) -> ()) -> BSProductChainable {
successClosure = closure
return self
}
func onFailure(closure: (FailureParams) -> ()) -> BSProductChainable {
failureClosure = closure
return self
}
func doSuccess(params: SuccessParams) {
if let closure = successClosure {
closure(params)
}
}
func doFailure(params: FailureParams) {
if let closure = failureClosure {
closure(params)
}
}
}
BSProductManagerSwift.swift
class BSProductManagerSwift: NSObject {
typealias productResponseChain = BSProductChainable<Product, NSError?>
typealias productsResponseChain = BSProductChainable<[Product], NSError?>
var serviceClient: BSNetworkingServiceClient!
var objectContext: NSManagedObjectContext!
var productChains: BSProductChainable<Product, NSError?>!
var productsChains: BSProductChainable<[Product], NSError?>!
convenience init(serviceClient: BSNetworkingServiceClient) {
self.init()
self.serviceClient = serviceClient
self.objectContext = managedObjectContext
self.productChains = BSProductChainable<Product, NSError?>()
self.productsChains = BSProductChainable<[Product], NSError?>()
}
func getProduct(ean: String) -> productResponseChain {
let urlString = BSConstants.BarcodeScanner.productEndpoint.stringByAppendingString(ean)
serviceClient.GET(urlString, failure: { (error) in
print("Could not get product")
}) { (response) in
if let json = response {
self.storeProduct(json).onSuccess({ (returedProduct) in
print("Stored product")
})
}
}
return productChains
}
func storeProduct(json: JSON) -> productResponseChain {
fetchProduct(json["ean"].stringValue).onSuccess { (returedProduct) in
self.productChains.doSuccess(returedProduct)
}
return productChains
}
func fetchProduct(ean: String) -> productResponseChain {
let fetchRequest = NSFetchRequest(entityName: "Product")
let predicateEAN = NSPredicate(format: "%K == %#", "ean", ean)
let predicateMarket = NSPredicate(format: "%K == %#", "market", BSCountryManager.sharedInstance().getCurrentCountry().market)
let predicateLocale = NSPredicate(format: "%K == %#", "locale", BSLocalizationManager.sharedManager().currentLocalization.localeIdentifier())
let predicateCurrency = NSPredicate(format: "%K == %#", "currency", BSLocalizationManager.sharedManager().currentLocalization.country.currencyIdentifierDMW)
let compoundPredicate = NSCompoundPredicate(andPredicateWithSubpredicates: [predicateEAN, predicateMarket, predicateLocale, predicateCurrency])
fetchRequest.predicate = compoundPredicate
do {
let matchingProuducts = try objectContext.executeFetchRequest(fetchRequest)
if matchingProuducts.count == 0 {
print("No matching products found")
let entity = NSEntityDescription.entityForName("Product", inManagedObjectContext: objectContext)
productChains.doSuccess(Product(entity: entity!, insertIntoManagedObjectContext: objectContext))
} else {
print("Found matching product")
let d = matchingProuducts.first as! Product
productChains.doSuccess(d)
}
} catch let error as NSError {
print("Could not fetch \(error), \(error.userInfo)")
productChains.doFailure(error)
}
return productChains
}
I initially initialised the chainable class per function but this had its own issues from which I thought (possibly incorrectly) that I should only initialise the chainable class once and pass around its reference.
Some input as to where I am going wrong/what I could try next would be great.

Answer 1

As recommended by #john elements, I decided to use PromiseKit
This didn't require to much of a code change and here are what the functions now look like (still need to do a bit of a code cleanup but it works!):
func getProduct(ean: String) -> Promise<Product> {
return Promise { fullfill, reject in
let urlString = BSConstants.BarcodeScanner.productEndpoint.stringByAppendingString(ean)
serviceClient.GET(urlString, failure: { (error) in
reject(error!)
}) { (response) in
if let json = response {
self.storeProduct(json).then ({ returnedProduct in
print("We stored the product: \(returnedProduct.ean)")
fullfill(returnedProduct)
}).error { returnedError in
print("We had a problem storing the product: \(returnedError)")
}
}
}
}
}
func storeProduct(json: JSON) -> Promise<Product> {
return Promise { fullfill, reject in
fetchProduct(json["ean"].stringValue).then ({ returnedProduct in
var storedProduct: Product!
var isNewProduct = false
print("Fetched Product: \(returnedProduct.ean)")
isNewProduct = returnedProduct.valueForKey("ean") == nil
storedProduct = returnedProduct
storedProduct.setValue(json["name"].stringValue, forKey: "name")
storedProduct.setValue(json["ean"].stringValue, forKey: "ean")
storedProduct.setValue(json["image"].stringValue, forKey: "image")
storedProduct.setValue(json["price"].doubleValue, forKey: "price")
storedProduct.setValue(json["status"].intValue, forKey: "status")
storedProduct.setValue(json["pdp"].stringValue, forKey: "pdp")
storedProduct.setValue(BSCountryManager.sharedInstance().getCurrentCountry().market, forKey: "market")
storedProduct.setValue(BSLocalizationManager.sharedManager().currentLocalization.localeIdentifier(), forKey: "locale")
storedProduct.setValue(BSLocalizationManager.sharedManager().currentLocalization.country.currencyIdentifierDMW, forKey: "currency")
do {
try self.objectContext.save()
print("Stored Product: \(returnedProduct.ean)")
fullfill(returnedProduct)
if isNewProduct {
NSNotificationCenter.defaultCenter().postNotificationName("DidAddScanEntry", object: nil)
}
} catch let error as NSError {
print("Could not save \(error), \(error.userInfo)")
reject(error)
}
}).error { returnedError in
print("We had a problem fetching the product: \(returnedError)")
reject(returnedError)
}
}
}
func fetchProduct(ean: String) -> Promise<Product> {
return Promise { fullfill, reject in
let fetchRequest = NSFetchRequest(entityName: "Product")
let predicateEAN = NSPredicate(format: "%K == %#", "ean", ean)
let predicateMarket = NSPredicate(format: "%K == %#", "market", BSCountryManager.sharedInstance().getCurrentCountry().market)
let predicateLocale = NSPredicate(format: "%K == %#", "locale", BSLocalizationManager.sharedManager().currentLocalization.localeIdentifier())
let predicateCurrency = NSPredicate(format: "%K == %#", "currency", BSLocalizationManager.sharedManager().currentLocalization.country.currencyIdentifierDMW)
let compoundPredicate = NSCompoundPredicate(andPredicateWithSubpredicates: [predicateEAN, predicateMarket, predicateLocale, predicateCurrency])
fetchRequest.predicate = compoundPredicate
do {
let matchingProuducts = try objectContext.executeFetchRequest(fetchRequest)
if matchingProuducts.count == 0 {
print("No matching products found")
let entity = NSEntityDescription.entityForName("Product", inManagedObjectContext: objectContext)
fullfill(Product(entity: entity!, insertIntoManagedObjectContext: objectContext))
} else {
print("Found matching product")
let d = matchingProuducts.first as! Product
fullfill(d)
}
} catch let error as NSError {
print("Could not fetch \(error), \(error.userInfo)")
reject(error)
}
}
}