ContentView.swift

import SwiftUI

struct DetailView: View {
    
    let customer: String
    
    var body: some View {
        Text(customer)
            .font(.largeTitle)
    }
}

struct ContentView: View {
    
    let customers = ["Alex", "Mary", "John"]
    @State var selectedCustomer: String?
    
    var body: some View {
        NavigationView {
            
            VStack {
                    
                CustomerListView(customers: customers) { customer in
                    selectedCustomer = customer
                    print(customer)
                }
                
                Text("Just for Display")
                
                CustomerListView(customers: customers)
                
                if let selectedCustomer = selectedCustomer {
                    NavigationLink(
                        destination: DetailView(customer: selectedCustomer),
                        isActive: .constant(true),
                        label: {
                            EmptyView()
                        })
                }
                
            }
            .onAppear(perform: {
                selectedCustomer = nil
            })
           
            .navigationTitle("Customers")
        }
        
    }
}

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

CustomerListView.swift

//
//  CustomerListView.swift
//  LearnSwiftUI
//
//  Created by Mohammad Azam on 1/17/21.
//

import SwiftUI

struct CustomerListView: View {
    
    let customers: [String]
    let onSelected: ((String) -> Void)?
    
    
    init(customers: [String], onSelected: ((String) -> Void)? = nil) {
        self.customers = customers
        self.onSelected = onSelected
    }
    
    var body: some View {
        List(customers, id: \.self) { customer in
            HStack {
                Text(customer)
                Spacer()
                
                if onSelected != nil {
                    Image(systemName: "chevron.right")
                }
                
            }.contentShape(Rectangle())
            .onTapGesture(perform: {
                if let onSelected = onSelected {
                    onSelected(customer)
                }
            })
        }.listStyle(PlainListStyle())
        
    }
}

struct CustomerListView_Previews: PreviewProvider {
    static var previews: some View {
        CustomerListView(customers: ["John", "Alex", "Mary"])
    }
}