使 @MainActor class 或 actor 符合 Codable

Question

如何将 Codable 一致性添加到需要与 MainActor 隔离的 class？

例如，下面的代码给出了编译器错误：

@MainActor final class MyClass: Codable {
    var value: Int
    
    enum CodingKeys: String, CodingKey {
        case value
    }
    
    init(from decoder: Decoder) throws { // <-- Compiler error: Initializer 'init(from:)' isolated to global actor 'MainActor' can not satisfy corresponding requirement from protocol 'Decodable'
        let data = try decoder.container(keyedBy: CodingKeys.self)
        self.value = try data.decode(Int.self, forKey: .value)
    }
    
    func encode(to encoder: Encoder) throws { // <-- Compiler error: Instance method 'encode(to:)' isolated to global actor 'MainActor' can not satisfy corresponding requirement from protocol 'Encodable'
        var container = encoder.container(keyedBy: CodingKeys.self)
        try container.encode(value, forKey: .value)
    }
}

我现在肯定在努力了解演员和@MainActor！

Answer 1

您提供的 class 没有任何内容需要与主要演员隔离，所以不要隔离 class 作为一个整体。如果还有其他您没有向我们展示的成员确实需要与主要演员隔离，请隔离他们。

示例：

final class MyClass: Codable {
    private var value: Int
    @MainActor init(value: Int) {
        self.value = value
    }
    @MainActor func setMyValue(to newValue:Int) {
        self.value = newValue
    }
    @MainActor func getMyValue() -> Int {
        self.value
    }
    enum CodingKeys: String, CodingKey {
        case value
    }
    init(from decoder: Decoder) throws {
        let data = try decoder.container(keyedBy: CodingKeys.self)
        self.value = try data.decode(Int.self, forKey: .value)
    }
    func encode(to encoder: Encoder) throws { // <-- Compiler error: Instance method 'encode(to:)' isolated to global actor 'MainActor' can not satisfy corresponding requirement from protocol 'Encodable'
        var container = encoder.container(keyedBy: CodingKeys.self)
        try container.encode(value, forKey: .value)
    }
}

使 @MainActor class 或 actor 符合 Codable

Conforming @MainActor class, or actor, to Codable

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