I have a class called Person:
class Person {
var firstName: String?
var lastName: String?
let birthPlace = "Belgium"
}
let person = [Person]()
Now the problem is I want to get all first names into a String array ([String]), how can I do it?
you can use flatMap for that:
let firstName = person.flatMap{ return $0.firstName }
flatMap? The array is not nested in any way.
flatMap will create an array of non-optional strings [String], that's what OP asked for. The firstName property is an optional (String?), so the result of map{ return $0.firstName} will be [String?].First of all, you should rewrite your Person class. firstName and lastName shouldn't be optional, since everyone has both a first and a last name and unless your app will specifically be made for people who were born in Belgium, hardcoding that as the birthPlace is also a bad idea.
Take the time and write an initializer for the class.
class Person {
var firstName: String
var lastName: String
let birthPlace: String
init(firstName: String, lastName: String, birthPlace: String){
self.firstName = firstName
self.lastName = lastName
self.birthPlace = birthPlace
}
}
You can use map to get an array of first names from an array of Person objects.
let people = [Person]()
let firstNames = people.map{$0.firstName}
firstNameandlastNameoptional? In practice everybody has a first and last name. Don't use optionals as an alibi not to write an initializer. That's very bad habit.