如何在 Swift 中使用另一个数组中的元素来过滤数组？

Question

我有两个数组

let toBeFiltered = ["star0", "star2", "star1", "star0", "star3", "star4"]
let theFilter = ["star1", "star3"]

如何使用第二个数组过滤第一个数组？实际上

theFilter

可以动态改变，例如，

let theFilter = ["star2"]
or maybe
let theFilter = ["star0", "star4", "star2"]

感谢您的帮助:)

Answer 1

使用 设置操作

Set(toBeFiltered).intersection(Set(theFilter))

了解更多：https://developer.apple.com/library/content/documentation/Swift/Conceptual/Swift_Programming_Language/CollectionTypes.html

Answer 2

let toBeFiltered = ["star0", "star2", "star1", "star0", "star3", "star4"]
let theFilter = ["star1", "star3"]

let filtered = toBeFiltered.filter(theFilter.contains)

Answer 3

您还可以过滤结构数组

struct myStruct
        {
          var userid:String;
          var details:String;
          init() {
            userid = "default value";
            details = "default";
          }

    };
    var f1 = myStruct();
    f1.userid = "1";
    f1.details = "Good boy";

    var f2 = myStruct();
    f2.userid = "2";
    f2.details = "Bad boy";

    var f3 = myStruct();
    f3.userid = "3";
    f3.details = "Gentleman";

    var arrNames1:Array = [f1,f3];

    var arrNames2:Array = [f3,f1,f2];

    let filteredArrayStruct =  arrNames1.filter( { (user: myStruct) -> Bool in
      return arrNames2.contains({ (user1: myStruct) -> Bool in
        return user.userid == user1.userid;
      })
    })
print(filteredArrayStruct)

对于 Set 必须符合 Hashable 协议

class mytestclass: Hashable
{
  var userid:Int ;
  var details:String;

  var hashValue: Int {
    return self.userid
  }
  init(userid: Int, details:String)
 {
  self.userid = userid;
  self.details = details;
  }
}
func ==(lhs: mytestclass, rhs: mytestclass) -> Bool {
  return lhs.userid == rhs.userid
}

var t1 = mytestclass(userid: 1,details: "Good boy");


var t2 = mytestclass(userid: 2,details: "bad boy");

var t3 = mytestclass(userid: 3,details: "gentle man");


var classArrayNames:Set<mytestclass> = [t1,t2];

var classArrayNames2:Set<mytestclass> = [t3,t1,t2];


 let result =  Set(classArrayNames).intersect(classArrayNames2)

Answer 4

这似乎是今天的一个主题:)建立在另一个很好的答案的基础上，我建议在

intersect(_:)

上使用

Set

方法：

let toBeFiltered = ["star0", "star2", "star1", "star0", "star3", "star4"]
let theFilter = ["star1", "star3"]
let filtered = Set(toBeFiltered).intersect(theFilter)

// => ["star1", "star3"] of type Set<String>

// ...if you actually need an array, you can get one using Array(filtered)

Answer 5

let mainArray = ["one", "two", "three", "three", "three", "four", "five"]
let miniArray = ["two", "three"]
let leftOvers = mainArray.filter( {miniArray.contains($0) == false} )
print(leftOvers)

Answer 6

虽然按照 Arsen 的建议使用 Sets 绝对是最优雅的，但有时你想保留 duplicates 和 order:

//: Playground - noun: a place where people can play

import Foundation

extension Collection where Element: Equatable {

    func intersection(with filter: [Element]) -> [Element] {
        return self.filter { element in filter.contains(element) }
    }

}

let toBeFiltered = ["star0", "star2", "star1", "star0", "star3", "star4", "star1"]
let theFilter = ["star1", "star3"]

let filtered = toBeFiltered.intersection(with: theFilter) // ["star1", "star3", "star1"]

Answer 7

您可以组合 Swift 中可用的过滤器和包含函数：

func filter(_ isInincluded: (Self.Element) throws -> Bool) re throws -> [Self.Element]

func contains(where predicate: (Self.Element) throws -> Bool) re throws -> Bool

contains：返回一个布尔值，指示序列是否包含满足给定谓词的元素。

struct Team {
 var id: String
 var name: String
 var logo: String
}

struct Matches {
 var date: String?
 var description: String?
 var name: String?
 var winner: String?
 var highlights: String?
}

var upcoming: [Matches] = []
var selectedTeams: [Team] = []
// Do filter
var filterUpcoming = upcoming.filter { matches in
   return selectedTeams.contains { team in
      return matches.name == team.name
   }
}