SwiftUI ForEach printing duplicate items - ios

Question

In my application I am creating various arrays of Identifiable structs using my API response. I am iterating over said array to build lists within the Content and Sidebar columns of my Navigation Split View. If I print the array before my ForEach call, the array is normal. When printing each item from within the ForEach (let _ = print(item)) the item prints twice. However the item is only added to the List once. Is this normal behavior? It appears to be happening with all of my ForEach calls. Visually the view looks correct, just want to be sure there isn’t any additional looping or view updated occurring.
Printing each item of array. Resulting in duplicate prints.
//
// TeamView.swift
// myDashboard
//
// Created by nl492k on 10/18/22.
//
import SwiftUI
struct TeamView: View {
var user: loggedInUser
var viewData = apiData()
// viewData is an instance of the apiData struct that includes 2 Arrays of identifieable structs ("gauges" & "trends") and a "team" struct that containts an array of idenfifiable structs "teamMembers" viewData is a singular object that is updated by the completion handler of my API call.
// struct apiData {
// var gauges : Array<gaugeObj>
// var trends : Array<trendObj>
// var team : teamObj
//
// init(gauges : Array<gaugeObj> = Array<gaugeObj>(), trends: Array<trendObj> = Array<trendObj>(), team: teamObj = teamObj()) {
// self.gauges = gauges
// self.trends = trends
// self.team = team
// }
// }
#Binding var uid_selection: String?
var emulation_uid: String
var body: some View {
if viewData.team.attuid == "" {
Label("Not Signed In", systemImage: "person.crop.circle.fill.badge.questionmark")
}
else {
List(selection: $uid_selection){
HStack {
NavigationLink(value: viewData.team.superv) {
AsyncImage(url: URL(string: "\(userImageUrl)\(viewData.team.attuid)")) { image in
image.resizable()
.clipShape(Circle())
.shadow(radius: 10)
.overlay(Circle().stroke(Color.gray, lineWidth: 2))
} placeholder: {
ProgressView()
}
.frame(width:30, height: 35)
VStack (alignment: .leading){
Text("\(viewData.team.fName) \(viewData.team.lName)")
Text("\(viewData.team.jobTitle)")
.font(.system(size: 10, weight: .thin))
}
}
Label("", systemImage:"arrow.up.and.person.rectangle.portrait")
}
Divider()
//------ This prints the Array of identifiable structs, as expected, with no issues --------
let _ = print(viewData.team.teamMembers)
ForEach(viewData.team.teamMembers) { employee in
//----- This prints multiple times per employee in array ------.
let _ = print(employee)
NavigationLink(value: employee.attuid) {
AsyncImage(url: URL(string: "\(userImageUrl)\(employee.attuid)")) { image in
image.resizable()
.clipShape(Circle())
.shadow(radius: 10)
.overlay(Circle().stroke(Color.gray, lineWidth: 2))
} placeholder: {
ProgressView()
}
.frame(width:30, height: 35)
VStack (alignment: .leading){
Text("\(employee.fName) \(employee.lName)")
Text("\(employee.jobTitle)")
.font(.system(size: 10, weight: .thin))
}
}
}
}
.background(Color("ContentColumn"))
.scrollContentBackground(.hidden)
}
}
}
struct TeamView_Previews: PreviewProvider {
static var previews: some View {
TeamView(user: loggedInUser.shared,
viewData: apiData(gauges:gaugesTest,
trends: trendsTest,
team: teamTest),
uid_selection: .constant(loggedInUser.shared.attuid),
emulation_uid: "")
}
}

Answer 1

From your code snippet, it looks like you're doing a print in the body of the ForEach, and seeing multiple prints per item.
Actually, this is completely normal behaviour because SwiftUI may render a view multiple times (which will cause your print statement to be called each time). There is no need to worry about such rerenders (unless you're debugging performance issues). SwiftUI's rendering heuristics isn't known to the public, and may sometimes choose to make multiple rendering passes even though no state variables have changed.