How to convert one array of objects to another in Swift?

In Swift, there are several ways to convert one array of objects to another array of objects. One way is to use a for-in loop and map the elements of the original array to the new array. The map function allows you to apply a transformation to each element of an array and returns a new array with the transformed elements.

struct Person {
    let firstName: String
    let lastName: String
}

let people = [Person(firstName: "John", lastName: "Doe"),
              Person(firstName: "Jane", lastName: "Smith")]

let fullNames = people.map { "\($0.firstName) \($0.lastName)" }
print(fullNames) // ["John Doe", "Jane Smith"]

Read more on The power of map in Swift and Map, FlatMap, Filter, Reduce – High order functions in Swift 5+

Another way to convert an array of objects is to use the compactMap function. This function works similarly to the map function, but it also filters out nil values.

struct Person {
    let firstName: String
    let lastName: String
    var fullName: String?
}

let people = [Person(firstName: "John", lastName: "Doe"),
              Person(firstName: "Jane", lastName: "Smith")]

let firstNames = people.compactMap { $0.firstName }
print(firstNames) // [John, Jane]

Another approach is to use the filter function, this function allows you to filter the elements of an array based on a certain condition and returns a new array with only the elements that match that condition

struct Person {
    let firstName: String
    let lastName: String
    let age: Int
}

let people = [Person(firstName: "John", lastName: "Doe", age: 30),
              Person(firstName: "Jane", lastName: "Smith", age: 25),
              Person(firstName: "Robert", lastName: "Johnson", age: 35)]

let adults = people.filter { $0.age >= 18 }
print(adults) // [Person(firstName: "John", lastName: "Doe", age: 30), Person(firstName: "Jane", lastName: "Smith", age: 25), Person(firstName: "Robert", lastName: "Johnson", age: 35)]

Lastly, you can also use the reduce function to convert one array of objects to another array of objects. The reduce function takes an initial value and a closure that takes two parameters. It applies the closure to the initial value and the first element of the array, then applies the closure to the result and the next element of the array, and so on.

struct Person {
    let firstName: String
    let lastName: String
}

let people = [Person(firstName: "John", lastName: "Doe"),
              Person(firstName: "Jane", lastName: "Smith")]

let initial: [String] = []
let fullNames = people.reduce(initial) { (result, person) in result + ["\(person.firstName) \(person.lastName)"] }
print(fullNames) // ["John Doe", "Jane Smith"]

All these methods will help you to convert an array of objects to another array of objects in Swift

✍️ Written by Ishtiak Ahmed

👉 Follow me on X ● LinkedIn

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