Decide to copy the interface and functionality from ios calculator app and got up to following stage. I`m trying to use lazyVgrid for buttons I can make exact same interface but without lazyVgrid...if you compile the code and run youll see that "0" is not in right shape. I tried roundedrectangle playing with cornerradius and frame width but each time I couldnt make it work with lazyVgrid.

I watched some videos on youtube who implemented calculator app nobody used lazygrids. Also functionality was overly complicated I tried to keep it simple.

Didnt finish functionality for percent,decimal and negative/positive sign. Thats why all calculations are done with Ints.

And other issue I`m trying to solve is the actual textfield that I used I want to keep it up to 9 chars as native calculator app is doing in portrait mode. I can fit some digits up to 9 chars but some cant fit I need a way to readjust the textfields frame or ???

3 files myButtons.swift for just array of buttons, ButtonView.swift for making views in foreach for each button, and contentView.

//
//  myButtons.swift
//  Calculator
//
//

import Foundation

let myButtons = [
    "AC","+/-","%","÷",
    "7","8","9","×",
    "4","5","6","−",
    "1","2","3","+",
    "0",".","="
]

//
//  ButtonsView.swift
//  Calculator
//
//

import SwiftUI

struct ButtonsView: View {
    var name:String
    var bgColor:Color{
        switch name {
        case "1","2","3","4","5","6","7","8","9","0",".":
            return Color(.systemGray2)
        case "AC","+/-","%":
            return Color(.systemGray4)
        default:
            return .orange
        }
    }

    var foregroundColor:Color{
        switch name {
        case "AC","+/-","%":
            return .black
        default:
            return .white
        }
    }

    var body: some View {
        RoundedRectangle(cornerRadius: 50)
            .fill(bgColor)
            .frame(width: 80, height: 80)
            .overlay(
            Text(name)
                .font(.largeTitle)
                .foregroundColor(foregroundColor)
            )

    }
}

struct ButtonsView_Previews: PreviewProvider {
    static var previews: some View {
        ButtonsView(name: "0")
    }
}

import SwiftUI

struct ContentView: View {
    @State private var displayNumber = ""
    @State private var operand1 = 0
    @State private var operand2 = 0
    @State private var calculation = ""
    @State private var secondOperation = false //redundant workaround to start load operand2

    let myGridItem = [GridItem(.flexible(minimum: 30, maximum: 100)),GridItem(.flexible(minimum: 30, maximum: 100)),GridItem(.flexible(minimum: 30, maximum: 100)),GridItem(.flexible(minimum: 30, maximum: 100))]

    var body: some View {
        ZStack {
            Color.black.edgesIgnoringSafeArea(.all)
            VStack{
                HStack{
                    TextField("", text: $displayNumber)
                        .font(.system(size: 70))
                        .multilineTextAlignment(.trailing)
                        .foregroundColor(.white)
                        .frame(minWidth:0,maxWidth: .infinity,maxHeight: 150)
                        .padding(.horizontal,5)
                }

                VStack{
                    LazyVGrid(columns: myGridItem, content: {
                        ForEach(myButtons,id:\.self){buttons in
                            ButtonsView(name: buttons)
                                .onTapGesture {
                                    checkOperation(input: buttons)
                                }
                        }
                    })
                }.padding()
            }
        }
    }

    func checkOperation(input: String){
        guard input != "AC" else {
            restart()
            return
        }

        guard input != "=" else{
            if calculation.isEmpty{
                return
            }
            else{
                switch calculation {
                case "+":
                    displayNumber = String(operand1 + operand2)
                    reset()
                case "-":
                    displayNumber = String(operand1 - operand2)
                    reset()
                case "*":
                    displayNumber = String(operand1 * operand2)
                    reset()
                case "÷":
                    displayNumber = String(operand1 / operand2)
                    reset()

                default:
                    print("hi there")
                }
            }
            return
        }

        if Int(input) != nil {
            sendToDisplay(input)
            return
        }

        if calculation.isEmpty{ //workaround to clear the display and start loading operand2
        calculation = input
            secondOperation = true
        }
        else{
            calculation = input
        }

    }

    func restart(){
        operand2 = 0
        operand1 = 0
        calculation = ""
        displayNumber = ""
    }

    func reset(){
        operand1 = 0
        operand2 = 0
        calculation = ""
    }
    func sendToDisplay(_ number:String){
        guard displayNumber.count <= 9 else {
            return
        }

        if secondOperation {
            displayNumber = ""
            secondOperation = !secondOperation
        }

        if calculation.isEmpty{
            displayNumber += number
            operand1 = Int(displayNumber)!
        }
        else{
            displayNumber += number
            operand2 = Int(displayNumber)!
        }

    }

}

struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        ContentView()
    }
}