JohnSundell

/**
 *  Copyright (c) John Sundell 2017
 *  Licensed under the MIT license
 */

import Foundation
import XCTest

/**
 *  Assert that an expression throws a given error

JohnSundell

func loadSearchData(matching query: String) throws -> Data {
    let urlString = "https://my.api.com/search?q=\(query)"
    
    guard let url = URL(string: urlString) else {
        throw SearchError.invalidQuery(query)
    }
    
    return try Data(contentsOf: url)
}

JohnSundell

func loadSearchData(matching query: String) throws -> Data {
    let urlString = "https://my.api.com/search?q=\(query)"
    
    guard let url = URL(string: urlString) else {
        throw SearchError.invalidQuery(query)
    }
    
    do {
        return try Data(contentsOf: url)
    } catch {

JohnSundell

func perform<T>(_ expression: @autoclosure () throws -> T,
                orThrow error: Error) throws -> T {
    do {
        return try expression()
    } catch {
        throw error
    }
}

JohnSundell

func loadSearchData(matching query: String) throws -> Data {
    let urlString = "https://my.api.com/search?q=\(query)"
    
    guard let url = URL(string: urlString) else {
        throw SearchError.invalidQuery(query)
    }
    
    return try perform(Data(contentsOf: url),
                       orThrow: SearchError.dataLoadingFailed(url))
}

JohnSundell

class ModelLoader<T: Unboxable & Requestable> {
    func load(completionHandler: (Result<T>) -> Void) {
        networkService.loadData(from: T.requestURL) { data in
            do {
                try completionHandler(.success(unbox(data: data)))
            } catch {
                let error = ModelLoadingError.unboxingFailed(error)
                completionHandler(.error(error))
            }
        }

JohnSundell

protocol ModelLoading {
    associatedtype Model
    
    func load(completionHandler: (Result<Model>) -> Void)
}

JohnSundell

class ViewController: UIViewController {
    init(modelLoader: ModelLoading) {
        ...
    }
}

JohnSundell

class ViewController: UIViewController {
    init<T: ModelLoading>(modelLoader: T) where T.Model == MyModel {
        ...
    }
}

JohnSundell

class AnyModelLoader<T>: ModelLoading {
    typealias CompletionHandler = (Result<T>) -> Void
    
    private let loadingClosure: (CompletionHandler) -> Void
    
    init<L: ModelLoading>(loader: L) where L.Model == T {
        loadingClosure = loader.load
    }
    
    func load(completionHandler: CompletionHandler) {