在自定义类上使用NSCoding时在self.init调用错误之前使用的'self' [英] 'self' used before self.init call error while using NSCoding on a custom class

问题描述

我正在尝试编码自定义类，因此可以使用NSKeyedArchiver.archivedDataWithRootObject

I'm trying to encode a custom class so I can save it using NSKeyedArchiver.archivedDataWithRootObject

但是当我尝试遵循NSCoding协议时，出现此错误:self.init之前使用了'self'.这是我的代码:

but when I try to conform to the NSCoding protocol, I get this error : 'self' used before self.init. Here is my code:

class MemberRewardsInfo: NSObject, NSCoding {
var id: Int?


  required convenience init?(coder aDecoder: NSCoder) {

    guard let unarchivedId = aDecoder.decodeObjectForKey("id") as? Int

      else {
        return nil
      } 
  }


  func encodeWithCoder(aCoder: NSCoder) {

    aCoder.encodeObject(id, forKey: "id")
  }
}

这很烦人，不确定为什么它不起作用.

its pretty annoying, not sure why it's not working.

推荐答案

该错误消息具有误导性，但是您需要将init(coder:)设置为指定的初始化程序.

The error message is sort of misleading, but you need to make init(coder:) a designated initializer.

您需要将init(code:)修改为以下内容:

You need to modify your init(code:) to something like this:

required init?(coder aDecoder: NSCoder) {
    guard let unarchivedId = aDecoder.decodeObjectForKey("id") as? Int else {
            return nil
    }
    self.id = unarchivedId
    super.init()
}

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