Passing search terms down to child view queries

[matiaskorhonen]

I'm trying to figure out the correct way of passing search terms from .searchable { … } in a parent view down to child views.

My code look something like this:

struct BarRequest: ValueObservationQueryable {
    let foo: Foo
    var searchText: String = ""

    static var defaultValue: [Bar] { [] }

    func fetch(_ db: Database) throws -> [Bar] {
        // Actually FTS but that's not relevant here
        try foo.bars.filter(Column("name").like("%\(searchText)%")).fetchAll(db)
    }
}

struct ParentView: View {
    var foos: [Foo]
    @State private var searchText: String

    var body: some View {
        LazyHStack {
            ForEach(foos, id: \.id) {
                ChildView(foo: $0).id($0.id)
            }.searchable(
                text: $searchText,
                prompt: "Search for a thing"
            )
        }
    }
}

struct ChildView: View {
    var foo: Foo

    @Query<BarRequest> private var bars: [Bar]

    init(foo: Foo) {
        self.foo = foo
        _items = Query(BarRequest(foo: foo))
    }

    var body: some View {
        List(childItems) { item in
            Text(childItems.name)
        }
    }
}

I'd like to pass the search terms to each child view so that they use them in their requests.

This is a UI where you can swipe between the child views so I'd like to avoid setting .searchable { … } on the child view level.

I can do that (and it works perfectly with a binding to $bars.searchTerms) but it comes with the side effect of resetting the search when swiping between the child views.

[groue]

Hello @matiaskorhonen,

I'd like to pass the search terms to each child view so that they use them in their requests.

Sure, let's do that:

 struct ParentView: View {
     var foos: [Foo]
     @State private var searchText: String
 
     var body: some View {
         LazyHStack {
             ForEach(foos, id: \.id) {
-                ChildView(foo: $0).id($0.id)
+                ChildView(foo: $0, searchText: searchText).id($0.id)
             }.searchable(
                 text: $searchText,
                 prompt: "Search for a thing"
             )
         }
     }
 }
 
 struct ChildView: View {
     var foo: Foo
 
     @Query<BarRequest> private var items: [Bar]
 
-    init(foo: Foo) {
+    init(foo: Foo, searchText: String) {
         self.foo = foo
-        _items = Query(BarRequest(foo: foo))
+        // Use the Query initializer that makes sure
+        // new items are fetched whenever foo or searchText change.
+        _items = Query(constant: BarRequest(foo: foo, searchText: searchText))
     }
 
     var body: some View {
         List(items) { item in
             Text(item.name)
         }
     }
 }

Note how I use the Query(constant:) initializer, so that ParentView is in full control, and a new database query is performed each time searchString is modified.

Without this constant parameter name, i.e. with a plain Query(BarRequest(foo: foo, searchText: searchText)), @Query behaves like @State. The request is tied to the lifetime of ChildView in the rendering tree, and the searchText argument is only interpreted as an initial search string.

See Initializing @Query from a Constant Request in the "Adding Parameters to Queryable Types" guide.

[matiaskorhonen]

Thanks! That's exactly what I needed.