Swift：在数组中查找值并返回特定键

Question

Im new to swift and would appreciate your help..

Problem:

In my future project I would love to look for a specific String in an Array and get only the names back who have this value in their hobbies Array.

My example:

struct Person {
var name: String
var hobbies:Set <String>
}

var persons: [Person]

persons = [

Person(name: "Steve", hobbies: ["PC", "PS4", "Gaming", "Basketball"]),
Person(name: "Max", hobbies: ["Gaming", "Xbox", "cooking", "PC"]),
Person(name: "Julia", hobbies: ["Soccer", "Tennis", "cooking", "Painting"])

]

var StringToSearch = "PC"

I would love to get only the names back who hobbies "PC" is. How can I iterate through my collection and get only the keys instead of the values back like in a dictionary? Thank you!

Answer 1

Use flatMap :

let result = persons.flatMap {
    $0.hobbies.contains(StringToSearch) ? $0.name : nil
}

Answer 2

Using filter(_:)

let stringToSearch = "PC"
let pcHobbiests = persons.filter { $0.hobbies.contains(stringToSearch) }
let pcHobbiestNames = persons.map { $0.name }

Explaination

filter(_:) will iterate over elements of a Sequence , building up a new Array containing only those elements for which closure evaluates to true. In this instance, the closure checks if the hobbies Array of the currently iteration's Person contains stringToSearch .

You can then iterate over your pcHobbiests Array or use them as you please:

for pcHobbiest in pcHobbiests {
    print(pcHobbiest)
}

Answer 3

you can use filter + map to return name array of all people who have "PC" hobbies:

let nameArray = persons.filter{$0.hobbies.contains("PC")}.map{$0.name}
//return ["Steve", "Max"]

Answer 4

Using reduce

After map , filter and flatMap here's my solution with reduce :)

let names = persons.reduce([String]()) { (names, person) -> [String] in
    guard person.hobbies.contains(keyword) else { return names }
    return names + [person.name]
}

One liner (but don't do it at home!)

And if your really want to write everything on 1 line...

let names = persons.reduce([String]()) { $0.0 + ($0.1.hobbies.contains(keyword) ? [$0.1.name] : []) }

Answer 5

Use Swift's for-in loop.

for pers in persons {
    if pers.hobbies.contains(StringToSearch) {
        nameOfPCGamer = pers.name
    }
}

Answer 6

You may use a loop, collect:

for p in persons {
  if p.hobbies.contains("PC") {
    // then you've got one!
  }
}

or you can use a more generic programming by filtering the array, thus obtaining an array of filtered content and iterating on it:

for p in persons.filter({$0.hoobies.contains("PC")}) {
  // got one...
}