Bind to a struct property in a SwiftUI Mac app - swift

Question

I'm building a macOS unit converter app in SwiftUI. In the example below, I have an acceleration view that has many text fields. These text fields represent different units of acceleration.
// AccelerationView.swift
struct AccelerationView: View {
#State private var accel = Acceleration()
#EnvironmentObject var formatter: Formatter
var body: some View {
VStack(alignment: .leading) {
Text("Metric").font(.subheadline)
HStack {
TextField("kilometer per second squared", value: $accel.kilometerPerSecondSquare, formatter: formatter.numberFormatter).frame(width: 120)
Text("km/s²").frame(width: 60, alignment: .leading)
}
HStack {
TextField("meter per second squared", value: $accel.meterPerSecondSquare, formatter: formatter.numberFormatter).frame(width: 120)
Text("m/s²").frame(width: 60, alignment: .leading)
}
HStack {
TextField("millimeter per second squared", value: $accel.millimeterPerSecondSquare, formatter: formatter.numberFormatter).frame(width: 120)
Text("mm/s²").frame(width: 60, alignment: .leading)
}
// and so on ...
}
.padding()
}
}
I would like to place the HStack into its own file to clean up the code in the view. My attempt at this is shown below:
// UnitTextField.swift
struct UnitTextField: View {
#State var value: Double = 0.0
let placeHolder: String
let label: String
var fieldWidth: CGFloat = 120
var labelWidth: CGFloat = 60
#EnvironmentObject private var formatter: Formatter
var body: some View {
HStack {
TextField(placeHolder, value: $value, formatter: formatter.numberFormatter)
.frame(width: fieldWidth)
.multilineTextAlignment(.trailing)
Text(label)
.frame(width: labelWidth, alignment: .leading)
}
}
}
This does not work because the UnitTextField value does not properly bind to the acceleration struct. I'm trying to accomplish something like this that I can use in the AccelerationView:
// AccelerationView.swift
struct AccelerationView: View {
#State private var accel = Acceleration()
#EnvironmentObject var formatter: Formatter
var body: some View {
VStack(alignment: .leading) {
Text("Metric").font(.subheadline)
UnitTextField(value: $accel.kilometerPerSecondSquare, placeHolder: "kilometer per second squared", label: "km/s²")
UnitTextField(value: $accel.meterPerSecondSquare, placeHolder: "meter per second squared", label: "m/s²")
UnitTextField(value: $accel.millimeterPerSecondSquare, placeHolder: "millimeter per second squared", label: "mm/s²")
// and so on ...
}
.padding()
}
}
Any suggestions on how to properly implement this in SwiftUI for a macOS application?

Answer 1

If to go from what you're going to accomplish (last snapshot), then I assume you need
struct UnitTextField: View {
#Binding var value: Double
instead of
struct UnitTextField: View {
#State var value: Double = 0.0

Answer 2

It could be like this with binding and environmentObject :
class MyFormat: Formatter, ObservableObject{
var numberFormat = NumberFormatter()
}
struct UnitTextField: View {
#Binding var value: Double
let placeHolder: String
let label: String
var fieldWidth: CGFloat = 120
var labelWidth: CGFloat = 60
#EnvironmentObject var formatter: MyFormat
var body: some View {
HStack {
TextField(placeHolder, value: $value, formatter: formatter.numberFormat)
.frame(width: fieldWidth)
.multilineTextAlignment(.trailing)
Text(label)
.frame(width: labelWidth, alignment: .leading)
}
}
}
struct Acceleration{
var kilometerPerSecondSquare : Double = 0.0
var meterPerSecondSquare : Double = 1.0
var millimeterPerSecondSquare : Double = 2.0
}
struct AccelerationView: View {
#State private var accel = Acceleration()
#EnvironmentObject var formatter: MyFormat
var body: some View {
VStack(alignment: .leading) {
Text("Metric").font(.subheadline)
UnitTextField(value: $accel.kilometerPerSecondSquare, placeHolder: "kilometer per second squared", label: "km/s²").environmentObject(formatter)
UnitTextField(value: $accel.meterPerSecondSquare, placeHolder: "meter per second squared", label: "m/s²").environmentObject(formatter)
UnitTextField(value: $accel.millimeterPerSecondSquare, placeHolder: "millimeter per second squared", label: "mm/s²").environmentObject(formatter)
// and so on ...
}
.padding()
}
}