Generic parameter 'Parent' could not be inferred - swift

Question

I'm working on my first Swift/SwiftUI project (other than the tutorials) and have run into what I think is a common problem -- the error Generic parameter 'Parent' could not be inferred -- toward the top of the view when the problem is actually with a List I'm trying to generate lower down in the form.
The app I'm building is a simple invoicing app: the user fills out the form fields and sends the invoice. An invoice can have multiple line items that the user enters one at a time and then are appended to a dictionary that should display inside the form.
This is the relevant variables from the top of the struct and the beginning of the view, where I hope I'm declaring the variables for line items correctly to modify them based on user input.
*Edited following #asperi's advice below.
#State private var lineItems = [LineItem]()
#State private var lineItem = LineItem()
struct LineItem: Codable, Hashable {
var productSku: String = ""
var productName: String = ""
var quantity: Double = 0
var unitPrice: Double = 0
}
func addLineItem(lineItem: LineItem){
lineItems.append(lineItem)
}
...
var body: some View {
NavigationView {
Form {
Section(header: Text("Customer Information")) { <-- error appears here
TextField("Customer Name", text: $customerName)
TextField("Customer Email", text: $customerEmail)
}
Here's the relevant portion of the form, where I'm trying to list all current line items and then allow the user to insert additional line items. I don't get any error until I add the List code, so I'm pretty sure I'm doing something wrong there.
Section(header: Text("Items")) {
List(lineItems, id: \.self) { item in
LineItemRow(lineItem: item)
Text(item.productName)
}
TextField("Product SKU", text: $productSKU)
TextField("Poduct Name", text: $productName)
TextField("Unit Price", text: $unitPrice, formatter: DoubleFormatter())
Picker("Quantity", selection: $quantity) {
ForEach(0 ..< 10) {
Text("\($0)")
}
}
Button(action: {
self.addLineItem(lineItem: LineItem(productSku:$productSKU,
productName:$productName,
quantity:$unitPrice,
unitPrice:$quantity))
print($lineItems)
}, label: {
Text("Add line item")
})
}
I've tested the button functionality in the console and it does seem to be appending to the dictionary correctly, but I need it to display as well.
I'm probably getting something very basic wrong with the List. Any advice?
For reference, here's the whole view:
struct AddInvoiceForm: View {
#State private var invoiceNumber: String = ""
#State private var _description: String = ""
#State private var dueDate: Date = Date()
#State private var sendImmediately: Bool = true
#State private var currency = 0
#State private var paymentType = 0
#State private var customerName: String = ""
#State private var customerEmail: String = ""
#State private var productSKU: String = ""
#State private var productName: String = ""
#State private var quantity: Int = 0
#State private var unitPrice: String = ""
#State private var lineItems = [LineItem]()
#State private var lineItem = LineItem()
struct LineItem: Codable, Hashable {
var productSku: String = ""
var productName: String = ""
var quantity: Double = 0
var unitPrice: Double = 0
}
func addLineItem(lineItem: LineItem){
lineItems.append(lineItem)
}
#State private var totalAmount: Double = 0.0
static let currencies = ["USD","GBP"]
var body: some View {
NavigationView {
Form {
Section(header: Text("Customer Information")) {
TextField("Customer Name", text: $customerName)
TextField("Customer Email", text: $customerEmail)
}
Section(header: Text("Invoice Information")) {
TextField("Invoice Number", text:$invoiceNumber)
TextField("Description", text:$_description)
DatePicker(selection: $dueDate, in: Date()..., displayedComponents: .date) {
Text("Due date")
}
Picker("Currency", selection: $currency) {
ForEach(0 ..< Self.currencies.count) {
Text(Self.currencies[$0])
}
}
}
Section(header: Text("Items")) {
List(lineItems, id: \.self) { item in
LineItemRow(lineItem: item)
Text(item.productName)
}
TextField("Product SKU", text: $productSKU)
TextField("Poduct Name", text: $productName)
TextField("Unit Price", text: $unitPrice, formatter: DoubleFormatter())
Picker("Quantity", selection: $quantity) {
ForEach(0 ..< 10) {
Text("\($0)")
}
}
Button(action: {
self.addLineItem(lineItem: LineItem(productSku:$productSKU,
productName:$productName,
quantity:$unitPrice,
unitPrice:$quantity))
print($lineItems)
}, label: {
Text("Add line item")
})
}
Section(header: Text("Totals")) {
Text("\(totalAmount)")
}
Section {
Button(action: {
print(Text("Send"))
}, label: {
Text("Send invoice")
})
}
}.navigationBarTitle("Invoice Details")
}
}
}

Answer 1

List(lineItems, id: \.productSku) { item in <-- I get the error when I add this
Your item is dictionary, but dictionary does not have .productSku key path, so the error.
I assume most simple & correct would be to make Item as struct
struct LineItem {
var productSku: String
...
}
...
#State private var lineItems = [LineItem]()
#State private var lineItem = LineItem()
...
List(lineItems, id: \.productSku) { item in