How can I Extract an Array from an Array of custom struct in Swift?

Question

I am making a struct called personStruct, which takes simple data like age and name. Here is this struct:

struct personStruct
{
    var name: String = String()
    var age: Int = Int()
}

then I am using this down class for extracting my wished arrays:

class PersonModel
{
    
    var persones: [personStruct] = [personStruct]()
    var countOfPersones: Int { persones.count }
    
    
    
    func personesAgeArray() -> [Int]
    {
        var returnArray: [Int] = [Int]()
        for item in persones { returnArray.append(item.age) }
        return returnArray
    }
    
    func personesNameArray() -> [String]
    {
        var returnArray: [String] = [String]()
        for item in persones { returnArray.append(item.name) }
        return returnArray
    }
   
}

And this is my use case of those struct and class:

let personModel: PersonModel = PersonModel()
personModel.persones = [personStruct(name: "bob", age: 30), personStruct(name: "Roz", age: 26), personStruct(name: "man", age: 40)]
print(personModel.personesAgeArray())
print(personModel.personesNameArray())

So as you see that class make that Job done!

My Goal: Do we have a real syntax or more efficiency way for making those Arrays? (I mean personesAgeArray and personesNameArray)

My Super Goal: I want personesAgeArray and personesNameArray get automatically builded/updated with adding new item to persones.

For a more "Swift" code: func personesAgeArray() -> [Int] { return persones.map{ $0.age }} maybe? But it's still working code to do a manual loop. For the rest, prefers using an uppercase for the first letter in struct and class names (personStruct -> PersonStruct), and naming might change. — Larme
– Larme, Commented Nov 16, 2020 at 15:34
I think you should forget about your super goal since it is overly complicated and will create a lot of overhead with little or no benefit. — Joakim Danielson
– Joakim Danielson, Commented Nov 16, 2020 at 15:45
@JoakimDanielson: I think so! but that would crazy if it would work? do you have any idea for me that I try? where I should start? — swiftPunk
– swiftPunk, Commented Nov 16, 2020 at 15:47
No, you would need to maintain 3 different properties and hence store data twice. A computed property is just as good — Joakim Danielson
– Joakim Danielson, Commented Nov 16, 2020 at 15:52
thanks! a lot! I think there is more costs than benefits! I forget it — swiftPunk
– swiftPunk, Commented Nov 16, 2020 at 15:54

Leo Dabus · Accepted Answer · 2020-11-16 15:42:26Z

2

struct Person {
    let name: String
    let age: Int
}

class Model {
    var people: [Person] = []
    var peopleCount: Int { people.count }
    var ages: [Int] { people.map(\.age) }
    var names: [String] { people.map(\.name) }
}

let model: Model = .init()
model.people = [.init(name: "bob", age: 30), .init(name: "Roz", age: 26), .init(name: "man", age: 40)]
print(model.ages)  // "[30, 26, 40]\n"
print(model.names) // "["bob", "Roz", "man"]\n"
model.people.append(.init(name: "Omid", age: 20))
print(model.ages)  // "[30, 26, 40, 20]\n"
print(model.names) // "["bob", "Roz", "man", "Omid"]\n"

answered Nov 16, 2020 at 15:42

Leo Dabus

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