Swift6之后更现代的REST API方法

技术总结
2.2k 词

目前网上检索到的关于Swift的REST API Call实现很多已经在swift6之后算是过时了的，Swift6强化了并发安全，以及URLsession API也相应增加了async版本（旧版本使用callback），更modern的方法是使用async/await以及Task来构建REST API Call

以下均使用URLsession进行REST API Call

在旧版Swift中, Get接口是这么call的

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    func fetchPage(completion: @escaping (Result<PageData, Error>) -> Void) {

    let url = URL(string: "http://127.0.0.1:8080/community/page/get")!

    URLSession.shared.dataTask(with: url) { data, response, error in

        if let error = error {
            completion(.failure(error))
            return
        }

        guard let data = data else {
            completion(.failure(URLError(.badServerResponse)))
            return
        }

        do {
            let result = try JSONDecoder().decode(PageData.self, from: data)
            completion(.success(result))
        } catch {
            completion(.failure(error))
        }

    }.resume()
}

大量使用了回调函数。
另外值得说的是在Swift6中xcode默认会给没有显式隔离的代码视作@MainActor,也就是默认跑主线程，所以在老式写法里对于let result = try JSONDecoder().decode(PageData.self, from: data)这里要在PageData的结构体上标注一个nonisolated

Swift6以后，新式Get Call 的async/await写法是这样的

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func fetchPage() async throws -> PageData {
    let url = URL(string: "http://127.0.0.1:8080/community/page/get")!
    let (data, _) = try await URLSession.shared.data(from: url)
    return try JSONDecoder().decode(PageData.self, from: data)
}

wrap的时候可以通过Task来执行它

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func load() {
    Task{
        let newPageData = try await fetchPage()
        ···
        ······
        ·········
    }
}

同样的这是Swift6之后现代版的Post Call

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func createTopic(title: String, content: String, time: Int64) async throws -> Topic {
    
    let newTopic = Topic(
        id: nil,
        title: title,
        content: content,
        create_time: time
    )
    
    guard let url = URL(string: "http://127.0.0.1:8080/community/page/addtopic") else {
        throw URLError(.badURL)
    }
    
    var request = URLRequest(url: url)
    request.httpMethod = "POST"
    request.setValue("application/json", forHTTPHeaderField: "Content-Type")
    
    request.httpBody = try JSONEncoder().encode(newTopic)
    
    let (data, response) = try await URLSession.shared.data(for: request)
    
    guard let httpResponse = response as? HTTPURLResponse,
          200..<300 ~= httpResponse.statusCode else {
        throw URLError(.badServerResponse)
    }
    
    return try JSONDecoder().decode(Topic.self, from: data)
}

wrap之后用Task执行也是和get同理

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