对 Unsplash api 的异步请求无法正常工作

如何解决对 Unsplash api 的异步请求无法正常工作

我的 swift 包 UnsplashSwiftUI 遇到了一些问题 在 WWDC 之前，我遇到了一些问题，导致我的 View 重新加载（正如您在主分支上看到的那样），但是当 async/await 被宣布时，这似乎是我的包的绝佳机会。

我正在开发分支上使用 async/await 处理包。

但是，我现在在处理异步 API 请求时遇到了一些问题。

这是我的最小可重现示例，我从异步函数 getURL() 的 catch 块中得到打印错误“无法获取图像”。我也尝试在内部使用异步调用任务。

//From this
.task {
    await getURL()
}

//To this
.task {
    async {
        await getURL()
    }
}

import SwiftUI
import PlaygroundSupport

struct ContentView: View {
    var body: some View {
        VStack {
            UnsplashRandom(clientId: "TSozaArCYtCWcXnnUkh4KvKJ5ZfmVOn_FYbIVVn76Ew")
                .frame(width: 500,height: 500)
        }
    }
}
PlaygroundPage.current.setLiveView(ContentView())

import SwiftUI

@available(iOS 15,OSX 12,*)
public struct UnsplashRandom: View {
    
    //MARK: Parameters
    //Required parameters
    var clientId: String //Unsplash API access key
    
    @State private var unsplashData: UnsplashData? = nil
    @State private var requestURL: URL? = nil
    
    //MARK: Init
    public init(clientId: String) {
        self.clientId = clientId
        
        let url = URL(string: "https://api.unsplash.com/")!
        
        guard var components = URLComponents(url: url.appendingPathComponent("photos/random"),resolvingAgainstBaseURL: true)
        else { fatalError("Couldn't append path component")}

        components.queryItems = [URLQueryItem(name: "client_id",value: clientId)]
        
        _requestURL = State(initialValue: components.url!)
    }
    
    //MARK: Body
    public var body: some View {
        //MARK: Main View
        ZStack(alignment: .bottomTrailing) {
            //MARK: Remote Image
            AsyncImage (url: URL(string: unsplashData?.urls!.raw! ?? "https://images.unsplash.com/photo-1626643590239-4d5051bafbcc?ixid=MnwxOTUzMTJ8MHwxfHJhbmRvbXx8fHx8fHx8fDE2MjY5Njc0MjI&ixlib=rb-1.2.1")!)
                .aspectRatio(contentMode: .fit)
        }
        .task {
            await getURL()
        }
    }
    
    func getURL() async {
        do {
            let (data,_) = try await URLSession.shared.data(from: requestURL!)
            unsplashData =  try JSONDecoder().decode(UnsplashData.self,from: data)
        } catch {
            print("Failed to fetch image")
        }
    }
}

import Foundation

// MARK: - UnsplashData
struct UnsplashData: Codable {
    let id: String?
    let createdAt,updatedAt,promotedAt: Date?
    let width,height: Int?
    let color,blurHash: String?
    let unsplashDataDescription: String?
    let altDescription: String?
    let urls: Urls?
    let links: UnsplashDataLinks?
    let categories: [String]?
    let likes: Int?
    let likedByUser: Bool?
    let currentUserCollections: [String]?
    let sponsorship: JSONNull?
    let user: User?
    let exif: Exif?
    let location: Location?
    let views,downloads: Int?

    enum CodingKeys: String,CodingKey {
        case id
        case createdAt = "created_at"
        case updatedAt = "updated_at"
        case promotedAt = "promoted_at"
        case width,height,color
        case blurHash = "blur_hash"
        case unsplashDataDescription = "description"
        case altDescription = "alt_description"
        case urls,links,categories,likes
        case likedByUser = "liked_by_user"
        case currentUserCollections = "current_user_collections"
        case sponsorship,user,exif,location,views,downloads
    }
}

// MARK: - Exif
struct Exif: Codable {
    let make,model,exposureTime,aperture: String?
    let focalLength: String?
    let iso: Int?

    enum CodingKeys: String,CodingKey {
        case make,model
        case exposureTime = "exposure_time"
        case aperture
        case focalLength = "focal_length"
        case iso
    }
}

// MARK: - UnsplashDataLinks
struct UnsplashDataLinks: Codable {
    let linksSelf,html,download,downloadLocation: String?

    enum CodingKeys: String,CodingKey {
        case linksSelf = "self"
        case html,download
        case downloadLocation = "download_location"
    }
}

// MARK: - Location
struct Location: Codable {
    let title,name,city,country: String?
    let position: Position?
}

// MARK: - Position
struct Position: Codable {
    let latitude,longitude: Double?
}

// MARK: - Urls
struct Urls: Codable {
    let raw,full,regular,small: String?
    let thumb: String?
}

// MARK: - User
struct User: Codable {
    let id: String?
    let updatedAt: Date?
    let username,firstName,lastName: String?
    let twitterUsername: String?
    let portfolioURL: String?
    let bio: String?
    let location: String?
    let links: UserLinks?
    let profileImage: ProfileImage?
    let instagramUsername: String?
    let totalCollections,totalLikes,totalPhotos: Int?
    let acceptedTos: Bool?

    enum CodingKeys: String,CodingKey {
        case id
        case updatedAt = "updated_at"
        case username,name
        case firstName = "first_name"
        case lastName = "last_name"
        case twitterUsername = "twitter_username"
        case portfolioURL = "portfolio_url"
        case bio,links
        case profileImage = "profile_image"
        case instagramUsername = "instagram_username"
        case totalCollections = "total_collections"
        case totalLikes = "total_likes"
        case totalPhotos = "total_photos"
        case acceptedTos = "accepted_tos"
    }
}

// MARK: - UserLinks
struct UserLinks: Codable {
    let linksSelf,photos,likes: String?
    let portfolio,following,followers: String?

    enum CodingKeys: String,likes,portfolio,followers
    }
}

// MARK: - ProfileImage
struct ProfileImage: Codable {
    let small,medium,large: String?
}

// MARK: - Encode/decode helpers

class JSONNull: Codable,Hashable {

    public static func == (lhs: JSONNull,rhs: JSONNull) -> Bool {
        return true
    }

    public var hashValue: Int {
        return 0
    }

    public func hash(into hasher: inout Hasher) {
        // No-op
    }

    public init() {}

    public required init(from decoder: Decoder) throws {
        let container = try decoder.singleValueContainer()
        if !container.decodeNil() {
            throw DecodingError.typeMismatch(JSONNull.self,DecodingError.Context(codingPath: decoder.codingPath,debugDescription: "Wrong type for JSONNull"))
        }
    }

    public func encode(to encoder: Encoder) throws {
        var container = encoder.singleValueContainer()
        try container.encodeNil()
    }
}

解决方法

在您的模型 UnsplashData 和 User 中，替换 Date？与字符串？。

在那之后，这就是我测试我的答案的方式：

import SwiftUI

@main
struct TestApp: App {
    var body: some Scene {
        WindowGroup {
            ContentView()
        }
    }
}

struct ContentView: View {
@State var unsplashData: UnsplashData?

var body: some View {
    VStack {
        if let unsplash = unsplashData {
            Text("user is \(unsplash.user?.name ?? "no name")")
        } else {
            Text("testing testing")
        }
    }
    .task {
        await getUnsplashData()
    }
}

func getUnsplashData() async {
    let fetchResponse: UnsplashData? = await fetchIt()
    if let theResponse = fetchResponse {
        self.unsplashData = theResponse
        print("\n-----> getUnsplashData: \(theResponse)")
    }
}
    
    func fetchIt<T: Decodable>() async -> T? {
        let url = URL(string: "https://api.unsplash.com/photos/random?client_id=TSozaArCYtCWcXnnUkh4KvKJ5ZfmVOn_FYbIVVn76Ew")!
        let request = URLRequest(url: url)
        do {
            let (data,response) = try await URLSession.shared.data(for: request)
            guard let httpResponse = response as? HTTPURLResponse,httpResponse.statusCode == 200 else {
                // throw URLError(.badServerResponse)   //  todo
                print(URLError(.badServerResponse))
                return nil
            }
            let results = try JSONDecoder().decode(T.self,from: data)
            return results
        }
        catch {
            return nil
        }
    }
 
}