What Am I doing wrong to call the detail page - json

Question

import SwiftUI
struct SchoolsDetailView: View {
var data: School
var body: some View {
VStack{
Text((data.properties.name)!)
.modifier(CustomTextM(fontName: "OpenSans-Regular", fontSize: 20, fontColor: Color.black))
Spacer()
(Text("(") + Text((data.properties.areaCode)!) + Text(")-") + Text((data.properties.phone)!))
.modifier(CustomTextM(fontName: "OpenSans-Regular", fontSize: 15, fontColor: Color.black))
(Text((data.properties.address)!) + Text(", ") + Text(data.properties.city!) + Text(", ") + Text(data.properties.state!))
.modifier(CustomTextM(fontName: "OpenSans-Regular", fontSize: 15, fontColor: Color.black))
}
}
}
struct SchoolsDetailView_Previews: PreviewProvider {
static var previews: some View {
NavigationStack{
SchoolsDetailView(data: SchoolModel().schools[2])
}
It keeps printing out array out of index. And if I do "SchoolModel().schools.first!", it prints out "Unexpectedly found nil while unwrapping an Optional value"
Not sure of what to do to call it. From the List View, it segues and shows the detail fine but on the detail page it keeps printing out error.

Answer 1

When wanting to support previews and using immutable data its best to pass in the simple types to the View rather than the rich model type, e.g.
struct SchoolsDetailView: View {
let name: String
let area: String
let address: String
This allows you to simply do:
struct SchoolsDetailView_Previews: PreviewProvider {
static var previews: some View {
SchoolsDetailView(name: "Test Name", area: "Test Area", address: "Test Address")
}
This has the added efficiency that body is only recomputed when the data actually displayed changes. Rather than it needlessly being recomputed when another property of the school changes which is not displayed.
Watch WWDC 2020 Structure your app for SwiftUI previews for more info, in particular the first example "First, we'll look at at an example of passing immutable, simple data types into a view that doesn't need to change the values."