使用NSCoding创建一个类

问题描述

在我的第一个项目中，我使用以下代码创建一个类：

in my first project I was creating a class using the following code:

import Foundation

class Rate { 
    var currency: String!
    var sellRate: String!
    var buyRate: String!

    init (data: NSDictionary) {
        self.currency = getStringFromJSON(data, key:"CurrencyName")
        self.sellRate = getStringFromJSON(data, key:"SellRate")
        self.buyRate = getStringFromJSON(data, key:"BuyRate")
    }

    func getStringFromJSON(data: NSDictionary, key: String) -> String {
        if let info = data[key] as? String {
            return info
        }
        return ""
    }
}

我正在摸索如何使用NSCoding更新代码。我需要使用NSKeyedArchiver，这就是为什么对象应符合NSCoding协议的原因。

I am scratching my head of how to update code to use NSCoding. I need to use NSKeyedArchiver that is why objects should conform to the NSCoding protocol.

我有在GitHub中找到的工作示例，但仍然无法编写工作代码。示例：

I have working example which I found in GitHub, but still I fail to write working code. Example:

class Book: NSObject, NSCoding {
    var title: String!
    var author: String!

    required convenience init(coder decoder: NSCoder) {
        self.init()

        self.title = decoder.decodeObjectForKey("title") as! String?
        self.author = decoder.decodeObjectForKey("author")as! String?
    }

    func encodeWithCoder(coder: NSCoder) {
        coder.encodeObject(self.title, forKey: "title")
        coder.encodeObject(self.author, forKey: "author")
    }   
}

推荐答案

尝试一下：

class Rate : NSObject, NSCoding {
    var currency: String!
    var sellRate: String!
    var buyRate: String!

    init (_ data: NSDictionary) {
        super.init()
        self.currency = getStringFromJSON(data, key:"CurrencyName")
        self.sellRate = getStringFromJSON(data, key:"SellRate")
        self.buyRate = getStringFromJSON(data, key:"BuyRate")
    }

    func getStringFromJSON(data: NSDictionary, key: String) -> String {
        if let info = data[key] as? String {
            return info
        }
        return ""
    }

    // NSCoding protocol implementation
    @objc func encodeWithCoder(coder : NSCoder) {
        coder.encodeObject(self.currency, forKey:"currency")
        coder.encodeObject(self.sellRate, forKey:"sellRate")
        coder.encodeObject(self.buyRate, forKey:"buyRate")
    }

    @objc required init(coder aDecoder: NSCoder) {
        self.currency = aDecoder.decodeObjectForKey("currency") as! String
        self.sellRate = aDecoder.decodeObjectForKey("sellRate") as! String
        self.buyRate = aDecoder.decodeObjectForKey("buyRate") as! String
    }
}

// Usage
let dict = [
    "CurrencyName": "USD",
    "SellRate": "1.12",
    "BuyRate": "1.1"
] 

let r1 = Rate(dict)

// Archive it
let data = NSKeyedArchiver.archivedDataWithRootObject(r1)

// Get it back
let r2 = NSKeyedUnarchiver.unarchiveObjectWithData(data) as! Rate
print(r2.currency)
print(r2.sellRate)
print(r2.buyRate)

更改为原始代码：

1. 数据 init 中的$ c>标签通过 _ 设置为可选。


2. 由于您的费率类现在是从 NSObject 继承的，因此必须调用 super.init（）


3. 为 NSCoding 协议添加了实现

1. The data label in your init was made optional with a _.
2. Because your Rate class inherits from NSObject now, it must call super.init()
3. Added implementation for NSCoding protocol

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