SwiftUi value into a let statement - dynamic

Question

I want to make this let dynamic to what is passed into the item property.
if I change the 'forResource' to a static name everything works. I just can't make it dynamic.
import SwiftUI
struct PdfDetailView: View {
#Binding var item: String
let documentURL = Bundle.main.url(forResource: $item, withExtension: "pdf")!
var body: some View {
VStack(alignment: .leading) {
Text("Pdf view")
.font(.largeTitle)
HStack(alignment: .top) {
Text("PDF Below)
.font(.title)
}
PDFKitView(url: documentURL)
}
}
}

Answer 1

Here is possible solution (of course assuming you make sure the URL is valid before creating PdfDetailView)
struct PdfDetailView: View {
#Binding var item: String
var body: some View {
VStack(alignment: .leading) {
Text("Pdf view")
.font(.largeTitle)
HStack(alignment: .top) {
Text("PDF Below")
.font(.title)
}
PDFKitView(url: Bundle.main.url(forResource: item, withExtension: "pdf")!)
}
}
}
and here is possible alternate if item string is not guaranteed to be valid
struct PdfDetailView: View {
#Binding var item: String
var body: some View {
let documentURL = Bundle.main.url(forResource: item, withExtension: "pdf")
return VStack(alignment: .leading) {
Text("Pdf view")
.font(.largeTitle)
HStack(alignment: .top) {
Text("PDF Below")
.font(.title)
}
if documentURL != nil {
PDFKitView(url: documentURL!)
}
}
}
}

Answer 2

You can pass it in init:
struct PdfDetailView: View {
let documentURL: URL
init(item: String) {
documentURL = Bundle.main.url(forResource: item, withExtension: "pdf")!
// you could handle errors here as well (instead of force unwrapping optionals)
}
...
}
And in some other View call it like:
PdfDetailView(item: "someItem")
In this other view your item property may be dynamic (eg. #State) but it doesn't have to be dynamic in the PdfDetailView.