在 do-try-catch 中解码到另一个 class 会产生编译错误

Question

我遇到了编译错误。我试图将 API 响应解码为自定义 class（实际上是结构）。我们的 API returns 几种类型的错误（有时它包含字符串，但有时它包含 returns 代码（元组 [String: Int]））所以如果第一次解码失败，我想解码成另一个class。

如果我尝试解码成一个 class，没关系，但如果我尝试解码成 catch 范围内的另一个 class，它会产生编译错误

Invalid conversion from throwing function of type '(Data?, URLResponse?, Error?) throws -> Void' to non-throwing function type '(Data?, URLResponse?, Error?) -> Void'

你知道怎么解决吗？

我正在使用 Swift5、Xcode 12.4

struct ErrorInfo: Codable {
    public let message: String?
    public let details: String?
    public let debugInformation: String?
}

struct ErrorInfoWithErrorCode: Codable {
    public let message: [String: Int] // this is the difference.
    public let details: String?
    public let debugInformation: String?
}

let request = URLRequest(url: URL(string: "https://www.google.com/")!)

let task = URLSession.shared.dataTask(with: request) { data, response, error in
    if let httpResponse = response as? HTTPURLResponse, !(200..<300).contains(httpResponse.statusCode) {
        do {
            let errorMessage = try decoder.decode(ErrorInfo.self, from: data)
            print(errorMessage)
        } catch  {
            let errorMessage = try decoder.decode(ErrorInfoWithErrorCode.self, from: data)
            print(errorMessage)
        } catch {
            fatalError()
        }
    }
}
task.resume()

playground 中的错误消息。

error: MyPlayground.playground:28:54: error: invalid conversion from throwing function of type '(Data?, URLResponse?, Error?) throws -> Void' to non-throwing function type '(Data?, URLResponse?, Error?) -> Void'
let task = URLSession.shared.dataTask(with: request) { data, response, error in

Answer 1

另一个嵌套try也需要一个do，你可以试试

do {
    let errorMessage = try decoder.decode(ErrorInfo.self, from: data)
    print(errorMessage)
} catch  {
    do {
        let errorMessage = try decoder.decode(ErrorInfoWithErrorCode.self, from: data)
        print(errorMessage)
    } catch {
        fatalError()
    }
}

在 do-try-catch 中解码到另一个 class 会产生编译错误

Decoding to another class in do-try-catch produces compile error

xcode

decode

swift