Build Better Apps Faster

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BUILD APPS

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PEOPLE TAKE APPS FOR GRANTED

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BUILD BETTER APPS FASTER PIERLUIGI CIFANI

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SOFTWARE HAS ALWAYS BEEN ABOUT BUILDING ABSTRACTIONS

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BIT -> BYTE BYTE -> ASSEMBLY ASSEMBLY -> C C -> OBJECTIVE C

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OBJECTIVE C -> SWIFT

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SWIFT ENABLES US TO BUILD ABSTRACTIONS THAT ARE CLOSER TO OUR PROBLEM DOMAIN

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≈ 60% OF THE CODE WE WRITE IS "JUST" REST CLIENT CODE

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WHAT WILL WE BUILD? 1. Generic UICollectionViewDataSource 2. Easy to reason networking

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1. GENERIC UICollectionViewDataSource

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GENERIC STATEFUL UICollectionViewDataSource

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SWIFT == STATELESS !

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IN SWIFT YOU CAN BE MORE EXPLICIT ABOUT THE STATE

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IN ANY UITableViewDataSource - (void)requestWithCompletionBlock:(AAPLCompletionBlock)block { self.executingRequest = YES; [self showLoadingView]; [self requestUsersWithPage:self.currentPagination completionBlock:^(NSArray *array, NSError *error) { if (error) { [self showError]; } else { self.array = array; [self.tableView reloadData]; } self.executingRequest = NO; block(array, error); }]; }

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public enum ListState { case Loading case Loaded(data: [T]) case Failure(error: ErrorType) }

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private func fetchData() { collectionView.state = .Loading searchUserInteractor.fetchLocationAndUsers() { [weak self] result in guard let strongSelf = self else { return } switch result { case .Failure(let error): strongSelf.collectionView.state = .Failure(error: error) case .Success(let users): strongSelf.collectionView.state = .Loaded(data: users) } } }

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However, last time I tried to do collectionView.state = .Loading this happened: error: value of type 'UICollectionView' has no member 'state' collectionView.state = .Loading ^~~~~~~~~~~~~~ ~~~~~ !!!!!!

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APPLE PROVIDES 3 POINTS OF CUSTOMIZATION: 1. Subclassing 2. UICollectionViewFlowLayout 3. UICollectionViewDataSource

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APPLE PROVIDES 3 POINTS OF CUSTOMIZATION: 1. Subclassing 2. UICollectionViewFlowLayout 3. UICollectionViewDataSource ✅

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OBJECTIVES: 1. Enforce MVVM1 2. Map one model object to one cell kind at compile time 3. Support for ListState 4. Customization for the .Loading and .Error state 5. Independence from any Layout 1 The one good thing that came out of Microsoft.

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ENFORCE MVVM public protocol ViewModelConfigurable { associatedtype VM func configureFor(viewModel viewModel: VM) -> Void } public protocol ViewModelReusable: ViewModelConfigurable { static var reuseType: ReuseType { get } static var reuseIdentifier: String { get } } public enum ReuseType { case NIB(UINib) case ClassReference(AnyClass) }

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//MARK:- Extensions extension ViewModelReusable where Self: UICollectionViewCell { public static var reuseIdentifier: String { return NSStringFromClass(self) } public static var reuseType: ReuseType { return .ClassReference(Self) } }

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MAP ONE MODEL OBJECT TO ONE CELL KIND AT COMPILE TIME

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class CollectionViewStatefulDataSource { typealias ModelMapper = (Model) -> (Cell.VM) weak var collectionView: UICollectionView? let mapper: ModelMapper var state: ListState { didSet { collectionView?.reloadData() } } }

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TO THE PLAYGROUND

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POSSIBLE IMPROVEMENTS: > Pull to refresh > Inifite scrolling > Support for n sections

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2. EASY TO REASON NETWORKING

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ConfigurationLogic *logic = [ConfigurationLogic currentConfiguration]; [NetworkFetcher callService:@"/users" host:[logic baseURL] method:GET postData:nil bodyInJSON:NO hasCache:YES timeoutInterval:[logic servicesTimeOut] successHandler:successHandler failureHandler:failureHandler];

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func lookForStockForSymbols (symbol : String, handler : FetchSymbolHandler?) -> StockFetcherOperation { let parameters = [ "input" : symbol ] let request = networkFetcher.request( .GET, "http://dev.markitondemand.com/Api/v2/Lookup/json", parameters:parameters , encoding:.URL ) request.responseJSON { (_, _, operationResult) -> Void in /** Some code */ } return StockFetcherOperation(request: request) }

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OBJECTIVES: 1. Composability 2. Sensitive default values 3. Readability 4. Self documented

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MORE PROTOCOLS

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/** Protocol used to describe what is needed in order to send REST API requests. */ public protocol Endpoint { /// The path for the request var path: String { get } /// The HTTPMethod for the request var method: HTTPMethod { get } /// Optional parameters for the request var parameters: [String : AnyObject]? { get } /// How the parameters should be encoded var parameterEncoding: HTTPParameterEncoding { get } /// The HTTP headers to be sent var httpHeaderFields: [String : String]? { get } }

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// This is the default implementation for Endpoint extension Endpoint { public var method: HTTPMethod { return .GET } var parameters: [String : AnyObject]? { return nil } public var parameterEncoding: HTTPParameterEncoding { return .URL } public var httpHeaderFields: [String : String]? { return nil } }

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enum AuthenticationAPI: Endpoint { case LoginFacebook(token: String) }

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extension AuthenticationAPI: Endpoint { var path: String { switch self { case .LoginFacebook(_): return "/authentication" } } var method: HTTPMethod { switch self { case .LoginFacebook(_): return .POST } } var parameters: [String : AnyObject]? { switch self { case .LoginFacebook(let token): return [ "token" : token ] } } }

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enum UsersAPI { case SearchUsers(Filter) case UserDetails(UUID) case UserPictures(UUID) }

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extension UsersAPI: Endpoint { public var path: String { switch self { case .SearchUsers(_): return "/users" case .UserDetails(let uuid): return "/users/\(uuid)" case .UserPictures(let uuid): return "/users/\(uuid)/pictures" } } public var parameters: [String : AnyObject]? { switch self { case .SearchUsers(let filter): var params = [String : AnyObject]() params["min_age"] = filter.minAge params["max_age"] = filter.maxAge params["min_dist"] = filter.minDistance params["max_dist"] = filter.maxDistance params["lat"] = filter.latitude params["long"] = filter.longitude return params default: return nil } } }

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WHERE'S THE NSURLRequest?

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"Apps interacting with web services are encouraged to have custom types conform to URLRequestConvertible as a way to ensure consistency of requested endpoints." -- @mattt2 2 Alamofire's Readme.

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/** Types adopting the `URLRequestConvertible` protocol can be used to construct URL requests. */ public protocol URLRequestConvertible { /// The URL request. var URLRequest: NSMutableURLRequest { get } } protocol Endpoint: URLRequestConvertible { /* The other stuff */ var URLRequest: NSMutableURLRequest { let request = NSMutableURLRequest(URL: NSURL(string: path)!) request.HTTPMethod = method.rawValue request.allHTTPHeaderFields = httpHeaderFields let requestTuple = parameterEncoding.encode(request, parameters: parameters) return requestTuple.0 } }

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POSSIBLE IMPROVEMENTS: > Multiple environments > Authentication tokens > Response parsing