NSPredicate NSUnknownKeyException - Swift 4.0

问题描述

我的当前代码如下:

class ViewController:UIViewController{

ovveride func viewDidLoad(){
 filterData()
}

func filterData(){
  var usersArray = [User(name:"John",userId:1),User(name:"Ed",userId:2),User(name:"Ron",userId:3)]

 let filteredData = (userArray as NSArray).filtered(using:NSPredicate(format: "userId=1"))
}
}

上面的代码抛出了如下异常(NSUnknownKeyException):

The above code throws throws the following Exception (NSUnknownKeyException):

对象类型 '[valueForUndefinedKey:]':
此类不符合键 userId 的键值编码.

Apple 的 filter(using:) 文档没有指定任何可能导致此问题的更改.

The document of Apple for filter(using:) does not specify any changes that could be causing this issue.

如何在 Swift 4.0 中使用 NSPredicate?

How can I use NSPredicate in Swift 4.0?

此外，根据要求，我尝试使用 @objc.但是，还是一样的错误.

Also, as requested, I tried using @objc. But, still the same error.

@objc
class User:NSObject{
 var name:String!
var userId:Int!

init(name:String,userId:Int){
self.name = name
self.userId = userId
}
}

收到针对此问题的进一步评论后，将 @objc 属性添加到 userId 时，我收到以下消息.属性不能被标记@objc，因为它的类型不能在Objective-C中表示

With Further Comments received for this question, on adding @objc attribute to the userId I receive the below message.property cannot be marked @objc because its type cannot be represented in Objective-C

@objc
class User:NSObject{
 @objc var name:String!
var userId:Int! //@objc here results in error 

init(name:String,userId:Int){
self.name = name
self.userId = userId
}
}

String 属性 NSPredicate 它完全可以正常工作.- 将@objc 添加到类- 另外，将@objc 添加到属性

String property NSPredicate it works completely fine.- Add @objc to class- Also, add @objc to property

推荐答案

为什么不直接使用 filter?它更像是Swift-y"，不涉及将数组转换为 NSArray.

Why not just use filter? It's much more "Swift-y" and doesn't involve converting your array to an NSArray.

let filteredData = usersArray.filter { $0.userId == 1 }

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