RxSwift | Best way to make consecutive network requests? - ios

Question

I've been practicing RxSwift recently, but I'm running into a problem in making network requests.
The question is how can I make consecutive network requests .
For example, in Github api, I should use https://api.github.com/user/starred/{\owner}/{\repository_name} to check if the user starred the repository or not.
It should be sent after I received the data requested but I'm having a hard time to implement this.
Here's what I've tried so far:
import RxSwift
// Struct used to encode response
struct RepositoryResponse: Codable {
let items: [Item]
enum CodingKeys: String, CodingKey {
case items
}
struct Item: Codable {
let fullName: String
enum CodingKeys: String, CodingKey {
case fullName = "full_name"
}
}
}
// Actual data for further use
struct Repository {
let item: RepositoryResponse.Item
var fullName: String {
return item.fullName
}
var isStarred: Bool
init(_ item: RepositoryData, isStarred: Bool) {
self.item = item
self.isStarred = isStarred
}
}
// Url components
var baseUrl = URLComponents(string: "https://api.github.com/search/repositories") // base url
let query = URLQueryItem(name: "q", value: "flutter") // Keyword. flutter for this time.
let sort = URLQueryItem(name: "sort", value: "stars") // Sort by stars
let order = URLQueryItem(name: "order", value: "desc") // Desc order
baseUrl?.queryItems = [query, sort, order]
// Observable expected to return Observable<[Repository]>
Observable<URL>.of((baseUrl?.url)!)
.map { URLRequest(url: $0) }
.flatMap { request -> Observable<(response: HTTPURLResponse, data: Data)> in
return URLSession.shared.rx.response(request: request)
}
.filter { response, data in
return 200..<300 ~= response.statusCode
}
.map { _, data -> [RepositoryResponse.Item] in
let decoder = JSONDecoder()
if let decoded = try? decoder.decode(RepositoryResponse.self, from: data) {
return decoded.items
} else {
print("ERROR: decoding")
return [RepositoryResponse.Item]()
}
}
.map { items -> [Repository] in
let repos = items.map { item -> Repository in
var isStarred: Bool?
/// I want to initialize Repository with isStarred value
/// What should I do in here?
return Repository(item, isStarred: isStarred)
}
return repos
}
What I planned to do is getting repositories by Github search api and then checking if the user has starred each repository.
So I made Repository struct which has two variables containing the name of repository and star status each.
A problem occurs right here. To initialize the Repository struct, I should get star status.
I've tried a completion way, but it seems return before completion returns value.
private func isRepoStarred(name: String, completion: #escaping (Bool) -> Void) {
let isStarredCheckerUrl = URL(string: "https://api.github.com/user/starred/\(name)")!
URLSession.shared.dataTask(with: isStarredCheckerUrl) { _, response, _ in
guard let response = response as? HTTPURLResponse else {
return
}
let code = response.statusCode
if code == 404 {
return completion(false)
} else if code == 204 {
return completion(true)
} else {
return completion(false)
}
}
}
Another way I've tried is making Single observable but don't know how to use this exactly.
func isRepoStarredObs(name: String) -> Single<Bool> {
return Single<Bool>.create { observer in
let isStarredCheckerUrl = URL(string: "https://api.github.com/user/starred/\(name)")!
let task = URLSession.shared.dataTask(with: isStarredCheckerUrl) { _, response, _ in
guard let response = response as? HTTPURLResponse else {
return
}
let code = response.statusCode
if code == 404 {
observer(.success(false))
} else if code == 204 {
observer(.success(true))
} else {
observer(.failure(NSError(domain: "Invalid response", code: code)))
}
}
task.resume()
return Disposables.create { task.cancel() }
}
}
If you have any ideas, please let me know. Thanks.

Answer 1

This gets the starred status:
func isRepoStarred(name: String) -> Observable<Bool> {
URLSession.shared.rx.data(request: URLRequest(url: URL(string: "https://api.github.com/user/starred/\(name)")!))
.map { data in
var result = false
// find out if repo is starred here and return true or false.
return result
}
}
and this is your search.
func searchRepositories() -> Observable<RepositoryResponse> {
var baseUrl = URLComponents(string: "https://api.github.com/search/repositories") // base url
let query = URLQueryItem(name: "q", value: "flutter") // Keyword. flutter for this time.
let sort = URLQueryItem(name: "sort", value: "stars") // Sort by stars
let order = URLQueryItem(name: "order", value: "desc") // Desc order
baseUrl?.queryItems = [query, sort, order]
return URLSession.shared.rx.data(request: URLRequest(url: baseUrl!.url!))
.map { data in
try JSONDecoder().decode(RepositoryResponse.self, from: data)
}
}
That's all you need to make requests.
To combine them you would do this:
let repositories = searchRepositories()
.flatMap {
Observable.zip($0.items.map { item in
isRepoStarred(name: item.fullName).map { Repository(item, isStarred: $0) }
})
}
In general, it's best to reduce the amount of code inside a flatMap as much as possible. Here's a version that breaks the code up a bit better. This version might also be a bit easier to understand what's going on.
let repositories = searchRepositories()
.map { $0.items }
let starreds = repositories
.flatMap { items in
Observable.zip(items.map { isRepoStarred(name: $0.fullName) })
}
let repos = Observable.zip(repositories, starreds) { items, starreds in
zip(items, starreds)
.map { Repository($0, isStarred: $1) }
}