Playground codes which search github repository using RxSwift

playground_rx_search_github_repository.swift

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import UIKit
import RxSwift
import RxCocoa
import PlaygroundSupport

// Definition
struct GithubRepository {
    let name: String
    let starCount: Int
    init(from dictionary: [String: Any]) {
        name = dictionary["full_name"] as! String
        starCount = dictionary["stargazers_count"] as! Int
    }
}
struct SearchResult {
    let repos: [GithubRepository]
    let totalCount: Int
    init?(from response: Any) {
        guard let response = response as? [String: Any],
            let reposDictionaries = response["items"] as? [[String: Any]],
            let count = response["total_count"] as? Int else { return nil }
        repos = reposDictionaries.compactMap({ GithubRepository(from: $0) })
        totalCount = count
    }
}
func searchRepos(keyword: String) -> Observable<SearchResult?> {
    let endPoint = "https://api.github.com"
    let path = "/search/repositories"
    let query = "?q=\(keyword)"
    let url = URL(string: endPoint + path + query)!
    let request = URLRequest(url: url)
    return URLSession.shared.rx
        .json(request: request)
        .map { SearchResult(from: $0) }
}

class SearchViewController: UIViewController {
    let searchField = UITextField()
    let totalCountLabel = UILabel()
    let reposLabel = UILabel()
    let disposeBag = DisposeBag()   //Disposableを保持しておいて、deinitされるタイミングで購読の破棄を一気に行う
                                    //ViewControllerが破棄されるタイミングで購読もすべて破棄される
    
    override func viewDidLoad() {
        super.viewDidLoad()
        view.backgroundColor = .gray
        setupSubviews()
        bind()
    }
    func setupSubviews() {
        searchField.frame = CGRect(x: 10, y: 10, width: 300, height: 20)
        totalCountLabel.frame = CGRect(x: 10, y: 40, width: 300, height: 20)
        reposLabel.frame = CGRect(x: 10, y: 60, width: 300, height: 500)
        
        searchField.borderStyle = .roundedRect
        searchField.keyboardType = .alphabet
        reposLabel.numberOfLines = 0

        [searchField, totalCountLabel, reposLabel]
            .forEach(view.addSubview(_:))
    }
}
extension SearchViewController {
    func bind() {
        
        let result: Observable<SearchResult?> = searchField.rx.text
            .orEmpty//Optional<String> -> String or ""
            .asObservable()// テキストフィールドの値が更新されるたびに、最新の値を排出する
            .skip(1)//最初に排出する値は無視する
            .debounce(0.3, scheduler: MainScheduler.instance)//直前の値から0.3秒以内に排出された次の値は無視
            .distinctUntilChanged()//直前の値と同じなら無視する
            .flatMapLatest{ searchRepos(keyword: $0)//新しい値だけの結果にする
                .observeOn(MainScheduler.instance)//以降の処理はメインスレッドで行う指定
                .catchErrorJustReturn(nil)//もしもエラーが排出された場合はnilを返す
                //エラーが排出されてもObservableシーケンスに値が流れ続けるようになる
        }.share(replay: 1)//connectable Observableへの変換
        // SearchResultからStringへの変換
        let foundRepos: Observable<String> = result.map {
            let repos = $0?.repos ?? [GithubRepository]()
            return repos.reduce("") {
                $0 + "\($1.name)(\($1.starCount))\n"
            }
        }
        // SearchResultからStringへの変換
        let foundCount: Observable<String> = result.map {
            let count = $0?.totalCount ?? 0
            return "TotalCount: \(count)"
        }
        
        //UIパーツへの束縛処理
        foundRepos
            .bind(to: reposLabel.rx.text)//レポジトリの名前とスター数の文字列をreposLabel.rx.textにバインドする
            .disposed(by: disposeBag)
        foundCount
            .startWith("Input Repository Name")//検索結果から生成する文字列が渡ってくるまで表示する値を指定
            .bind(to: totalCountLabel.rx.text)//検索結果数をtotalCountLabel.rx.textにバインドする
            .disposed(by: disposeBag)
    }
}
//PlaygroundPage.current.liveView = SearchViewController()

let parent = UIViewController()
let vc = SearchViewController()
vc.view.layoutIfNeeded()
parent.view.translatesAutoresizingMaskIntoConstraints = false
vc.view.translatesAutoresizingMaskIntoConstraints = false
parent.addChildViewController(vc)
parent.view.addSubview(vc.view)

NSLayoutConstraint.activate([
    vc.view.leadingAnchor.constraint(equalTo: parent.view.leadingAnchor),
    vc.view.trailingAnchor.constraint(equalTo: parent.view.trailingAnchor),
    vc.view.topAnchor.constraint(equalTo: parent.view.topAnchor),
    vc.view.bottomAnchor.constraint(equalTo: parent.view.bottomAnchor)
    ]
)

let traits = UITraitCollection(
    traitsFrom: [
        UITraitCollection(verticalSizeClass: .compact),
        UITraitCollection(horizontalSizeClass: .compact),
        UITraitCollection(preferredContentSizeCategory: .extraExtraExtraLarge)
    ]
)
parent.setOverrideTraitCollection(traits, forChildViewController: vc)
parent.preferredContentSize = parent.view.frame.size
PlaygroundPage.current.liveView = parent
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