In my app I'm trying to get this next button to keep getting new pages. When i press next 501 loads and when I press prev 499 loads. I'm understanding that it's because comicNumber is set to 500, but having troubles with how I can make it keep going (502,503 etc).
This is my api call
struct Comic: Codable {
var month: String
var num: Int
var link: String
var year: String
var news: String
var safe_title: String
var transcript: String
var alt: String
var img: String
var title: String
var day: String
}
enum ApiError: Error {
case dataIsNil
}
class ApiCall {
var comicNumber: Int
init(comicNumber: Int) {
self.comicNumber = comicNumber
}
func getComic(completion: @escaping (Result<Comic, Error>) -> ()) {
guard let url = URL(string: "https://xkcd.com/\(comicNumber)/info.0.json") else {return}
URLSession.shared.dataTask(with: url) { data, _, error in
if let error = error {
print(error)
completion(.failure(error))
return
}
guard let data = data else {
print("data is nil")
completion(.failure(ApiError.dataIsNil))
return
}
do {
let comic = try JSONDecoder().decode(Comic.self, from: data)
// print(comic)
DispatchQueue.main.async {
completion(.success(comic))
}
} catch {
print(error)
completion(.failure(error))
}
}
.resume()
}
func getNextComic(completion: @escaping (Result<Comic, Error>) -> ()) {
guard let url = URL(string: "https://xkcd.com/\(comicNumber)/info.0.json") else {return}
URLSession.shared.dataTask(with: url) { data, _, error in
if let error = error {
print(error)
completion(.failure(error))
return
}
guard let data = data else {
print("data is nil")
completion(.failure(ApiError.dataIsNil))
return
}
do {
let comic = try JSONDecoder().decode(Comic.self, from: data)
DispatchQueue.main.async {
completion(.success(comic))
}
} catch {
print(error)
completion(.failure(error))
}
}
.resume()
}
func getPrevComic(completion: @escaping (Result<Comic, Error>) -> ()) {
guard let url = URL(string: "https://xkcd.com/\(comicNumber)/info.0.json") else {return}
URLSession.shared.dataTask(with: url) { data, _, error in
if let error = error {
print(error)
completion(.failure(error))
return
}
guard let data = data else {
print("data is nil")
completion(.failure(ApiError.dataIsNil))
return
}
do {
let comic = try JSONDecoder().decode(Comic.self, from: data)
DispatchQueue.main.async {
completion(.success(comic))
}
} catch {
print(error)
completion(.failure(error))
}
}
.resume()
}
}
And this is my View
struct ComicContainer: View {
@State var comic: Comic?
@State var comicNumber = 500
var body: some View {
ZStack {
VStack {
NavigationLink(destination: ComicDetailView(), label: {
AsyncImage(url: URL(string: comic?.img ?? "Hello")) { image in
image
.resizable()
.scaledToFit()
} placeholder: {
Color.purple.opacity(0.1)
}
.padding()
})
.onAppear {
ApiCall(comicNumber: comicNumber).getComic{ result in
switch result {
case .success(let comic):
self.comic = comic
case .failure(let error):
print(error)
}
}
}
.toolbar {
ToolbarItemGroup(placement: .bottomBar) {
CustomButton {
ApiCall(comicNumber: comicNumber - 1).getPrevComic{ result in
switch result {
case .success(let comic):
self.comic = comic
print(comic.num)
case .failure(let error):
print(error)
}
}
} content: {
Text("Prev")
}
Spacer()
Text("Comic num: \(comic?.num ?? 0)")
.padding()
Spacer()
CustomButton {
ApiCall(comicNumber: comicNumber 1).getNextComic{ result in
switch result {
case .success(let comic):
self.comic = comic
print(comic.num)
case .failure(let error):
print(error)
}
}
} content: {
Text("Next")
}
}
}
.navigationBarTitle("\(comic?.title ?? "title")")
}
}
}
}
I tried so the comicNumber gets 1 or - 1 when you press next or prev buttons
ApiCall(comicNumber: comicNumber 1).getNextComic{
I also tried with 1 inside the api but its just the same.
guard let url = URL(string: "https://xkcd.com/\(comicNumber 1)/info.0.json") else {return}
Does anyone have any guidance on how I could get this to work or what I'm doing wrong? I'm learning Swift and would really appreciate some help<3
CodePudding user response：
comicNumber is being stored in too many places. In SwiftUI we try to keep a "single source of truth". Keep an instance of ApiCall() as a member of your view so that comicNumber stays updated:
struct ComicContainer: View {
@State var comic: Comic?
var api = ApiCall(comicNumber: 500)
var body: some View {
ZStack {
VStack {
NavigationLink(destination: ComicDetailView(), label: {
AsyncImage(url: URL(string: comic?.img ?? "Hello")) { image in
image
.resizable()
.scaledToFit()
} placeholder: {
Color.purple.opacity(0.1)
}
.padding()
})
.onAppear {
apiCall.getComic{ result in
switch result {
case .success(let comic):
self.comic = comic
case .failure(let error):
print(error)
}
}
}
.toolbar {
ToolbarItemGroup(placement: .bottomBar) {
CustomButton {
apiCall.getPrevComic{ result in
switch result {
case .success(let comic):
self.comic = comic
print(comic.num)
case .failure(let error):
print(error)
}
}
} content: {
Text("Prev")
}
Spacer()
Text("Comic num: \(comic?.num ?? 0)")
.padding()
Spacer()
CustomButton {
apiCall.getNextComic{ result in
switch result {
case .success(let comic):
self.comic = comic
print(comic.num)
case .failure(let error):
print(error)
}
}
} content: {
Text("Next")
}
}
}
.navigationBarTitle("\(comic?.title ?? "title")")
}
}
}
}
And handle the updating of comicNumber within the view model (ApiCall):
class ApiCall {
var comicNumber: Int
init(comicNumber: Int) {
self.comicNumber = comicNumber
}
func getComic(completion: @escaping (Result<Comic, Error>) -> ()) {
guard let url = URL(string: "https://xkcd.com/\(comicNumber)/info.0.json") else {return}
URLSession.shared.dataTask(with: url) { data, _, error in
if let error = error {
print(error)
completion(.failure(error))
return
}
guard let data = data else {
print("data is nil")
completion(.failure(ApiError.dataIsNil))
return
}
do {
let comic = try JSONDecoder().decode(Comic.self, from: data)
// print(comic)
DispatchQueue.main.async {
completion(.success(comic))
}
} catch {
print(error)
completion(.failure(error))
}
}
.resume()
}
func getNextComic(completion: @escaping (Result<Comic, Error>) -> ()) {
// this
comicNumber = 1
getComic(completion: completion)
}
func getPrevComic(completion: @escaping (Result<Comic, Error>) -> ()) {
// this
comicNumber -= 1
getComic(completion: completion)
}
}