SwiftUI How to use class with function in view

Question

I have this simple class:

import Foundation

class Utility {
    func somma(int1:String, int2:String) -> String {
        let totale = (Int(int1) ?? 0) + (Int(int2) ?? 0)
        let totale_Str = String(totale)
        return totale_Str
    }
}

and this simple view:

import SwiftUI

struct ContentView: View {
    @State private var int1:String = "0"
    @State private var int2:String = "0"

    @State private var somma:String = ""

    var body: some View {
        VStack {
            TextField("Intero 1", text: $int1)
            TextField("Intero 2", text: $int2)
            Text("\(somma)")
            Button(action: {
                self.somma = Utility.somma(self.int1, self.int2)
            }) {
                Text("Somma")
            }
        }
    }
}

but in the line self.somma = Utility.somma(self.int1, self.int2) I have this error Instance member 'somma' cannot be used on type 'Utility'; did you mean to use a value of this type instead? I have tried in different ways to eliminate the error without finding the solution. How can I eliminate this error?

Either make the somma function static or create an instance of Utility. This is not SwiftUI related but a generic Swift design principle as in all other OO languages I know. Did you miss this or is there something SwiftUI related I overlooked? — berni
– berni, Commented Oct 30, 2019 at 22:14

Cesare Piersigilli · Accepted Answer · 2019-10-30 22:40:32Z

2

I found the solution. Simply change:

self.somma = Utility.somma(self.int1, self.int2)

with:

self.somma = Utility().somma(int1: self.int1, int2: self.int2)

answered Oct 30, 2019 at 22:40

Cesare Piersigilli

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Comments

Andrew · Accepted Answer · 2019-10-30 22:41:26Z

1

Class function in Swift are preceded with static keyword, so if you want to use somma as class (i.e static) function you have to declare it like this:

static func somma(int1:String, int2:String) -> String { //etc.

edited Oct 30, 2019 at 22:41

Andrew

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answered Oct 30, 2019 at 22:25

LuLuGaGa

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1 Comment

Cesare Piersigilli Over a year ago

I tried to do as you suggested, but it doesn't work.

Daviswww · Accepted Answer · 2020-04-18 13:27:11Z

0

Class:

import Foundation

class Utility:ObservableObject {
    var totale_Str : String = ""
    func somma(int1:String, int2:String) -> String {
        let totale = (Int(int1) ?? 0) + (Int(int2) ?? 0)
        let totale_Str = String(totale)
        return totale_Str
    }
}

View:

import SwiftUI

struct ContentView: View {
    @State private var int1:String = "0"
    @State private var int2:String = "0"

    @State private var somma : String = ""
    @ObservedObject var utility = Utility()
    var body: some View {
        VStack {
            TextField("Intero 1", text: $int1)
            TextField("Intero 2", text: $int2)
            Text("\(somma)")
            Button(action: {
                self.somma = utility.somma(int1: self.int1, int2: self.int2)
            }) {
                Text("Somma")
            }
        }
    }
}

answered Apr 18, 2020 at 13:27

Daviswww

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2 Comments

Interior Night Over a year ago

Could you explain your answer? e.g. why is this better (or not) than Cesare Piersigilli's own answer.

Daviswww Over a year ago

I just wanted to solve the problem, and I didn't notice that he had solved it.

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