Unable to use a defined state variable in the init() - swift

Question

I am trying to implement a search bar in my app, as now I want to use the keyword typed in the search bar to make an API call to fetch backend data, here is my code:
struct SearchView: View {
#State private var searchText : String=""
#ObservedObject var results:getSearchList
init(){
results = SearchList(idStr: self.searchText)
}
var body: some View {
NavigationView {
VStack {
SearchBar(text: $searchText)
}.navigationBarTitle(Text("Search"))
}
}
}
I implement SearchBar view followed the this tutorial https://www.appcoda.com/swiftui-search-bar/ exactly,
and getSearchList is a class which has an var called idStr,
struct searchResEntry: Codable, Identifiable{
var id:Int
var comment:String
}
class SearchList: ObservableObject {
// 1.
#Published var todos = [searchResEntry]()
var idStr: String
init(idStr: String) {
self.idStr = idStr
let url = URL(string: "https://..." + idStr)!
// 2.
URLSession.shared.dataTask(with: url) {(data, response, error) in
do {
if let todoData = data {
// 3.
let decodedData = try JSONDecoder().decode([searchResEntry].self, from: todoData)
DispatchQueue.main.async {
self.todos = decodedData
}
} else {
print("No data")
}
} catch {
print("Error")
}
}.resume()
}
}
the problem I am struggling now is that I want to use the variable searchText to initialize the getSearchList , getSearchList has an var called idStr, this idStr is to used to store the typed keyword, my code always get an error: 'self' used before all stored properties are initialized , I have no idea how to deal with this.

Answer 1

Here is your code, edited by me:
struct SearchView: View {
#StateObject var results = SearchList()
var body: some View {
NavigationView {
VStack {
SearchBar(text: $results.searchText)
}.navigationBarTitle(Text("Search"))
}
}
}
struct SearchResEntry: Codable, Identifiable {
var id:Int
var backdrop_path:String
}
class SearchList: ObservableObject {
#Published var todos = [SearchResEntry]()
#Published var searchText: String = ""
var cancellable: AnyCancellable?
init() {
cancellable = $searchText.debounce(
for: .seconds(0.2),
scheduler: RunLoop.main
).sink { _ in
self.performSearch()
}
}
func performSearch() {
if let pathParam = searchText.addingPercentEncoding(withAllowedCharacters: .urlPathAllowed),
let url = URL(string: "https://hw9node-310902.uc.r.appspot.com/mutisearch/\(pathParam)") {
URLSession.shared.dataTask(with: url) {(data, response, error) in
do {
if let todoData = data {
let decodedData = try JSONDecoder().decode([SearchResEntry].self, from: todoData)
DispatchQueue.main.async {
self.todos = decodedData
}
} else {
print("No data")
}
} catch {
print("Error")
}
}.resume()
} else {
print("Invalid URL")
}
}
}
Explanation
You are free to reverse the optional changes i made, but here are my explanations:
Use capital letter at the beginning of a Type's name. e.g write struct SearchResEntry, don't write struct searchResEntry. This is convention. Nothing big will happen if you don't follow conventions, but if anyone other than you (or maybe even you in 6 months) look at that code, chances are they go dizzy.
Dont start a Type's name with verbs like get! Again, this is just a convention. If anyone sees a getSomething() or even GetSomething() they'll think thats a function, not a Type.
Let the searchText be a published property in your model that performs the search. Don't perform search on init, instead use a function so you can initilize once and perform search any time you want (do results.performSearch() in your View). Also you can still turn your searchText into a binding to pass to your search bar (look at how i did it).
EDIT answer to your comment
I could right-away think of 3 different answers to your comment. This is the best of them, but also the most complicated one. Hopefully i chose the right option:
As you can see in the class SearchList i've added 2 things. First one is a cancellable to store an AnyCancellable, and second is the thing in init() { ... }. In init, we are doing something which results in an AnyCancellable and then we are storing that in the variable that i added.
What am i doing In init?
first $searchText gives us a Publisher. Basically, the publisher is called whenever the searchText value changes. Then you see .debounce(for: .seconds(0.2), on: RunLoop.main) which means only let the latest input go through and reach the next thing (the next thing is .sink { } as you can see), only if the user has stopped writing for 0.2 seconds. This is very helpful to avoid a load of requests to the server which can eventually make servers give you a 429 Too Many Requests error if many people are using your app (You can remove the whole .debounce thing if you don't like it). And the last thing is .sink { } which when any value reaches that point, it'll call the performSearch func for you and new results will be acquired from the server.
Alternative way
(again talking about your comment)
This is the simpler way. Do as follows:
remove init() { ... } completely if you've added it
remove var cancellable completely if you've added it
in your SearchView, do:
.onChange(of: results.searchText) { _ in
results.performSearch()
}
pretty self-explanatory; it'll perform the search anytime the searchText value is changed.