Prevent NavigationLink from processing state variable - ios

Question

I don't like my title, but it's the best I could think of. Basically, I have two Views: SearchInput and SearchResultList. The user enters a search term with SearchInput, taps "Go" and then sees the results of the search with SearchResultList. The code is:
struct SearchInput: View {
#State private var searchTerm: String = ""
var searchResult: [RTDocument] {
return RuntimeDataModel.shared.fetchRTDocuments(matching: self.searchTerm)
}
var body: some View {
NavigationView {
VStack {
TextField("Enter search term...", text: self.$searchTerm)
NavigationLink(destination: SearchResultList(
rtDocuments: self.searchResult
)) { Text("Go") } //NavigationLink
} //VStack
} //NavigationView
} //body
} //SearchInput
The issue I'm having is that every time the user enters a character in TextField, the bound-state variable searchTerm is updated which causes NavigationLink to reevaluate its destination -- which causes a Core Data fetch up in the computed searchResult variable.
I'd like the fetch to happen only once, when the user taps "Go". Is there a way to accomplish that?

Answer 1

This is expected behaviour, so in general you should redesign your SearchResultList, but this can help as a walkaround:
Declare a state on your input:
#State var shouldNavigate = false
Then separate the button form the navigation link.
Group {
Button("Go") {
self.shouldNavigate = true
}
NavigationLink(destination: Text("SearchResultList"),
isActive: $shouldNavigate) {
EmptyView()
}
}