反思和类型检查选项

玩 swift 2.0中的反射我正在尝试键入检查子值.

问题：任何项目的镜像中的子数组的每个元素都不是可选的,但是他的类型可以是可选的……当然,即使值为nil,我也会有子值

也许它不清楚,所以我在这里放一些代码来解释更好.

为方便起见,我在Mirror扩展中定义了一个下标,用于获取具有给定标签的子对象

extension Mirror {
    public subscript(key: String)->Child?{
        var child = children.filter {
            var valid = false
            if let label = $0.label {
                valid = label == key
            }
            return valid
            }.last
        if child == nil,let superMirror = superclassMirror() {
                child = superMirror[key]
        }
        return child
    }
}

完美,现在让我说我有这个课程

class Rule: NSObject,AProtocol {
    var hello: String?
    var subRule: Rule?
}

好的,现在问题

let aRule = Rule()
let mirroredRule = Mirror(reflecting:aRule)
if let child = mirroredRule["subRule"] {
     //child.value always exists
     //i can't do child.value is AProtocol? because child.value is not optional
     //child.value is AProtocol of course returns false
     //child.dynamicType is Optional(Rule)
     if let unwrapped = unwrap(child.value) where unwrapped is AProtocol {
         //This of course works only if child.value is not nil
         //so the unwrap function returns an unwrapped value
         //this is not a definitive solution
     }
}

child.value尚未初始化,所以它是nil,我无法使用unwrap函数检查他的类型.我正在编写一个反序列化器,所以我需要检查var是否为nil,因为在字典中将用于反序列化,它可以被定义.

private func unwrap(subject: Any) -> Any? {
    var value: Any?
    let mirrored = Mirror(reflecting:subject)
    if mirrored.displayStyle != .Optional {
        value = subject
    } else if let firstChild = mirrored.children.first {
        value = firstChild.value
    }
    return value
}

我希望问题很清楚.有什么建议？

解决方法

基于 this answer,我建议使用if case Optional< Any> .some(_).

我最近做了一些事情,以确保我的结构上至少有一个可选集.你可以粘贴到游乐场：

struct ErrorResponse: Codable {
    let message: String?
    let authorizationException: [String: String]?
    let validationException: String?
    let generalException: String?

    var isValid: Bool {
        var hasAtLeastOneNonNilErrorValue = false
        Mirror(reflecting: self).children.forEach {
            if case Optional<Any>.some(_) = $0.value {
                hasAtLeastOneNonNilErrorValue = true
            }
        }
        return hasAtLeastOneNonNilErrorValue
    }
}

let errorTest = ErrorResponse(message: "some message",authorizationException: nil,validationException: nil,generalException: nil)
let errorTest2 = ErrorResponse(message: nil,generalException: nil)

print("is valid: \(errorTest.isValid)")  //is valid: true
print("is valid: \(errorTest2.isValid)") //is valid: false