如何使用Swift 2.0和反射获取属性名称及其值?

问题描述：

给出此模型:

public class RSS2Feed {

    public var channel: RSS2FeedChannel?

    public init() {}
}

public class RSS2FeedChannel {   

    public var title: String?
    public var description: String?

    public init() {}

}

我需要做什么才能获取RSS2FeedChannel实例的属性名称和值?

What would I need to do in order to get the property names and values of an RSS2FeedChannel instance?

这就是我要尝试的:

let feed = RSS2Feed()
feed.channel = RSS2FeedChannel()
feed.channel?.title = "The Channel Title"

let mirror = Mirror(reflecting: feed.channel)
mirror.children.first // ({Some "Some"}, {{Some "The Channel Title...

for (index, value) in mirror.children.enumerate() {
    index // 0
    value.label // "Some"
    value.value // RSS2FeedChannel
}

最终，我正在尝试使用反射创建一个与实例匹配的Dictionary，但是到目前为止，我无法获得实例的属性名称和值.

Ultimately, I'm trying to create a Dictionary that matches the instance, using reflection, but so far I'm unable to get the properties name and values of the instance.

文档说:

在适当的时候可以使用可选标签，例如表示存储属性或活动枚举大小写的名称，当将字符串传递给后代方法时将用于查找.

The optional label may be used when appropriate, e.g. to represent the name of a stored property or of an active enum case, and will be used for lookup when Strings are passed to the descendant method.

但是我只得到一个"Some"字符串.

Yet I only get a "Some" string.

此外，当我希望每个子对象都是反映实例结构的元素"时，value属性将返回类型为RSS2FeedChannel的字符串！

Also, the value property is returning a string with the Type RSS2FeedChannel when I would expect each children to be "An element of the reflected instance's structure."!

答

当我理解正确时，这应该可以解决您的问题:

When i understand correct this should solve ur problem:

func aMethod() -> Void {
    let feed = RSS2Feed()
    feed.channel = RSS2FeedChannel()
    feed.channel?.title = "The Channel Title"
//  feed.channel?.description = "the description of your channel"

    guard  let channel = feed.channel else {
        return
    }

    let mirror = Mirror(reflecting: channel)
    for child in mirror.children {
        guard let key = child.label else {
            continue
        }
        let value = child.value

        guard let result = self.unwrap(value) else {
            continue
        }

        print("\(key): \(result)")
    }
}

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
}

快速3进行一些小的更改，

just some little changes for swift 3:

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
}

如何使用Swift 2.0和反射获取属性名称及其值?

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