Swift Talk Episode 1 - Networking

swift-talk-episode1-networking.swift

import Foundation


let url = URL(string:"http://localhost/test1.json")!
typealias JSONDictionary = [String:AnyObject]


// 资源的链接 & 解析闭包
struct Resource<A>{
    let url: URL
    let parse : (Data) -> A?
}



// 返回数据的结构体

struct Episode {
    let id : String
    let title: String
}

extension Episode{
    init?(dictionary:JSONDictionary) {
        guard let id = dictionary["id"] as? String, let title = dictionary["title"] as? String else { return nil }
        self.id = id
        self.title = title
    }
}

// 服务器 相当于你有资源 让别人来帮你加载 解析还是你来
final class WebService {
    func load<A>(resource:Resource<A>, completion:@escaping (A?) -> ()) {
        URLSession.shared.dataTask(with: resource.url) { (data, _, _) in
            guard let data = data else {
                completion(nil)
                return
            }
            completion(resource.parse(data))
            }.resume()
    }
}

extension Sequence {
    public func failingFlatMap<T>( transform: (Self.Iterator.Element) throws -> T?) rethrows -> [T]? {
        var result: [T] = []
        for element in self {
            guard let transformed = try transform(element) else { return nil }// 一旦有错误 直接跳出
            result.append(transformed)
        }
        return result
    }
}

extension Resource {
    init(url:URL,parseJSON:@escaping (AnyObject) -> A?) {
        self.url = url
        self.parse = { data in
            let json = try? JSONSerialization.jsonObject(with: data, options: [])
            return (json as AnyObject?).flatMap(parseJSON)
        }
    }
}


let episodesResource = Resource<[Episode]>(url:url,parseJSON:{
    json in
    guard let dictionaries = json as? [JSONDictionary] else {return nil}
    return dictionaries.flatMap(Episode.init)
})


var results :[Episode]? = []

WebService().load(resource: episodesResource) { (result) in
    results = result
    //print(result)
}
Thread.sleep(forTimeInterval: 10) // 为了足够的时间获取到结果 再退出
print(results)