Updating SwiftUI view from DB - swift

Question

I am trying to update a view fro a database. As the user types into a field, on each keypress an SQL query is fired that returns a list of items to display.
The problem I have is that the key pres causes the view to redraw and then the DB query changes the data in the view.
I have looked at future and promise but dont understand the swift versions (OK with Java and Scala concurrency).
I have tried using an Observalble instead of a state but get all kinds of problems with that also.
I think I am trying to do this the wrong way but can t think of a better way to try.
It would be nice if I could call the DB method asynchronously and get it to update the data array sometime in the future but just cant work out how to do it or an alternative method.
It might be that I am triggering the DB query from the wrong place, triggers at the start of the view body. The keypress updates an #State variable which triggers the redraw, a List is used to display each field of the DB records held in an array in Text objects. it all works perfectly with static data.
As you can see below not exactly the most complex thing.
struct CompanySearchView: View {
#ObservedObject var viewRouter: ViewRouter
#State private var name: String = ""
#ObservedObject var companys: Companys = nil
var body: some View {
incSearch()
return VStack(spacing: 12){
Text("Company Search")
.font(.headline)
HStack(spacing: 12){
Text("Company name")
.font(.headline)
TextField("Company name", text: $name)
.textFieldStyle(RoundedBorderTextFieldStyle())
}
List(companys.data){item in
Text(item.name)
}
}
.frame(minWidth: 480, minHeight: 300)
}
func incSearch(){
let connection = Connection(logger: self.viewRouter.logger!)
viewRouter.logger!.info("Search string \(name)");
companys.data = connection.search(n: name)
}
}
Many Thanks

Answer 1

struct CompanySearchView: View {
#ObservedObject var viewRouter: ViewRouter
#State private var name: String = ""
#ObservedObject private var companys: Companys
init(viewRouter: ViewRouter){
self.viewRouter = viewRouter
companys = Companys(router: viewRouter)
}
var body: some View {
companys.changeName(newName: name)
return VStack(spacing: 12){
Text("Company Search")
.font(.headline)
HStack(spacing: 12){
Text("Company name")
.font(.headline)
TextField("Company name", text: $name, onEditingChanged: { (changed) in
self.companys.changing = changed
})
.textFieldStyle(RoundedBorderTextFieldStyle())
}
List(companys.data){item in
Text(item.name)
}
}
.frame(minWidth: 480, minHeight: 300)
}
}
struct CompanySearchView_Previews: PreviewProvider {
static var previews: some View {
CompanySearchView(viewRouter: ViewRouter())
}
}
class Companys: ObservableObject {
private var name: String = ""
private let router: ViewRouter
var changing: Bool = false
#Published var data: [Company] = []
init(router: ViewRouter){
self.router = router
}
func changeName(newName: String){
if changing && name != newName {
name = newName;
let connection = Connection(logger: self.router.logger!)
router.logger!.info("Search string \(name)");
connection.search(n: name).then {
result in
self.data = result
print(result)
}
}
}
}
The main problem this solves (there may be better ways) is that when the original code run the first thing it did was run the DB request then render the view, no real problem there except it did a query that returned all companies and but the display remained blank. This is soled using the flag in the companys class set when the editing starts.
Now unless the field is being edited no search is done.
Using a Future the search is now performed asynchronously and updates the Companys class data which is published so that causes the view to be rendered.
Its not perfect as if the query executes very fast it is possible for the observed object to be updated before the current render g=has completed and back to square one.