ios - 如何使用 ObjectMapper 将自定义 Enum/RawRepresentable 映射到字典？

Question

使用以下简化结构:

class Property: Mappable {
    var path: String?

    override func mapping(map: Map) {
        path <- map["path"]
    }
}

class Specification {
    enum Name: String {
        case Small = "SMALL"
        case Medium = "MEDIUM"
    }
}

class ItemWithImages: Mappable {
    var properties: [Specification.Name : Property]?

    override func mapping(map: Map) {
        properties <- (map["properties"], EnumTransform<Specification.Name>())
    }
}

... 使用该 JSON:

[{"properties: ["SMALL": {"path": "http://..."}, "MEDIUM": {"path": "http://..."}]}]

... 使用 EnumTransform() 作为 Transform 时会产生以下(合理的)编译错误:

Binary operator '<-' cannot be applied to operands of type '[Specification.Name : Property]?' and '(Map, EnumTransform<Specification.Name>)'

那么自定义 TransformType 必须是什么样子才能以正确的方式映射该字典？

您可以在这里找到 EnumTransform 的源代码:https://github.com/Hearst-DD/ObjectMapper/blob/master/ObjectMapper/Transforms/EnumTransform.swift

谢谢!

Answer 1

TransformTypes 恕我直言，主要设计用于转换值而不是键。而且您的示例有点复杂，因为即使值也不仅仅是基本类型。

你觉得这个小技巧怎么样？

struct ItemWithImages: Mappable {
    var properties: [Specification.Name : Property]?

    init?(_ map: Map) {
    }

    mutating func mapping(map: Map) {
        let stringProperties: [String: Property]?
        // map local variable
        stringProperties <- map["properties"]

        // post process local variable
        if let stringProperties = stringProperties {
            properties = [:]
            for (key, value) in stringProperties {
                if let name = Specification.Name(rawValue: key) {
                    properties?[name] = value
                }
            }
        }
    }
}