create objects/instances in variables swift

Question

I don't know how to use variables when creating Instances or adressing them in Swift: For exmaple how do I do following in a loop (creating Instances):

class Guest {
    let name: String
    var age: Int 
    init(name: String, age: Int) {
        self.name = name
        self.age = age
    }
}

let guests = [["ann", 1] , ["bob", 2] ...]

so that the loop equals :

let ann = Guest(name: "ann" , age: 1)
let bob = Guest(name: "bob" , age: 2)
...

edit: I am looking for something like this:

for i in guests {
  let i[0] = Guest(name: i[0] , age: i[1])

Example for adressing:

print(guests[0].age)
>>>1

I've searched a lot but am getting directed to issues regarding creating variables in classes.

Thank you very much!

Your question is very vague, please try to edit it so we can help you. — Mo Abdul-Hameed
– Mo Abdul-Hameed, Commented Aug 31, 2017 at 20:35
@PEEJWEEJ yes I've tried, swift in terminal raises following error: repl.swift:11:10: error: consecutive statements on a line must be separated by ';' Where the "mistake pointer" points to the "i[0]" in let i[0] = .... — sryimnew
– sryimnew, Commented Aug 31, 2017 at 20:47
Oh for one. you're mutating your guests array which you can't do. You need to set it to a new array. See Charles Srstka's anwer — GetSwifty
– GetSwifty, Commented Aug 31, 2017 at 20:51

Charles Srstka · Accepted Answer · 2017-08-31 22:07:36Z

2

You can do that with a classic loop:

let input = [("Ann", 1), ("Bob", 2)]

var guests: [Guest] = []
for each in input {
    guests.append(Guest(name: each.0, age: each.1))
}

However, it can be done more concisely (and with avoidance of var) using functional techniques:

let guests = [("Ann", 1), ("Bob", 2)].map { Guest(name: $0.0, age: $0.1) }

EDIT: Dictionary-based solution (Swift 4; for Swift 3 version just use the classic loop)

let input = [("Ann", 1), ("Bob", 2)]
let guests = Dictionary(uniqueKeysWithValues: input.map {
    ($0.0, Guest(name: $0.0, age: $0.1))
})

Or, if it's possible for two guests to have the same name:

let guests = Dictionary(input.map { ($0.0, Guest(name: $0.0, age: $0.1)) }) { first, second in
    // put code here to choose which of two conflicting guests to return
    return first
}

With the dictionary, you can just do:

if let annsAge = guests["Ann"]?.age {
    // do something with the value
}

edited Aug 31, 2017 at 22:07

answered Aug 31, 2017 at 20:45

Charles Srstka

17.1k3 gold badges37 silver badges65 bronze badges

Sign up to request clarification or add additional context in comments.

8 Comments

Alexander Over a year ago

I would ditch the foreach loop altogether

Charles Srstka Over a year ago

I wanted to demonstrate the increased conciseness of the functional approach via the contrast.

sryimnew Over a year ago

Close :) - but i still don't have Ann.age

Charles Srstka Over a year ago

Huh? Yes, you do, with both of them.

sryimnew Over a year ago

print(Ann.age) gives me "error: use of unresolved identifier 'Ann' " I can only do print(guests[0].age) -or?

|

Ramanpreet Singh · Accepted Answer · 2017-09-01 05:41:21Z

0

   //MARK: Call method to create multiple instances 

createInstance([("Ann", 1), ("Bob", 2)])

func createInstance(_ input: Array<Guest>) {        
    for each in input {
        guests.append(Guest(name: each.0, age: each.1))
    }
}

answered Sep 1, 2017 at 5:41

Ramanpreet Singh

914 bronze badges

Collectives™ on Stack Overflow

create objects/instances in variables swift

2 Answers 2

8 Comments

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

8 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related