Swift6之后更现代的REST API方法

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) {
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        let url = URL(string: "http://127.0.0.1:8080/community/page/get")!
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        URLSession.shared.dataTask(with: url) { data, response, error in
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            if let error = error {
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                completion(.failure(error))
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                return
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            }
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            guard let data = data else {
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                completion(.failure(URLError(.badServerResponse)))
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                return
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            }
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            do {
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                let result = try JSONDecoder().decode(PageData.self, from: data)
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                completion(.success(result))
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            } catch {
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                completion(.failure(error))
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            }
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        }.resume()
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    }

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

wrap的时候可以通过Task来执行它

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

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

wrap之后用Task执行也是和get同理