Add cache

TAT/CurriculumViewController.swift

@@ -20,7 +20,7 @@ final class CurriculumViewController: UIViewController {
 
   private lazy var activityIndicator: UIActivityIndicatorView = {
     let activityIndicator = UIActivityIndicatorView(style: .whiteLarge)
-    activityIndicator.color = .blue
+    activityIndicator.color = .systemPink
     return activityIndicator
   }()
 
@@ -82,8 +82,10 @@ final class CurriculumViewController: UIViewController {
   }
 
   private func bindViewModel() {
+    let viewDidLoadTrigger = Observable.just(())
+    let searchTrigger = Observable.merge(viewDidLoadTrigger, leftBarItem.rx.tap.asObservable())
     let input = CurriculumViewModel.Input(targetStudentId: Observable.just("104440026"),
-                                          searchTrigger: leftBarItem.rx.tap.asObservable())
+                                          searchTrigger: searchTrigger)
     let output = viewModel.transform(input: input)
 
     output.state
@@ -99,9 +101,10 @@ final class CurriculumViewController: UIViewController {
 
     output.semesters
       .subscribe(onNext: { [weak self] (semesters) in
-        print(semesters)
         let semsterString = semesters.map { "\($0.year) 學年 第\($0.semester)學期" }
         self?.updateTitleView(by: semsterString)
+      }, onError: { (error) in
+          print(error)
       })
       .disposed(by: rx.disposeBag)
 
@@ -119,12 +122,12 @@ final class CurriculumViewController: UIViewController {
   }
 
   private func setUpLayouts() {
-    setUpActivityIndicator()
     setUpCollectionView()
+    setUpActivityIndicator()
   }
 
   private func setUpActivityIndicator() {
-     view.addSubview(activityIndicator)
+     collectionView.addSubview(activityIndicator)
      activityIndicator.snp.makeConstraints { (make) in
        make.center.equalToSuperview()
      }

TAT/ViewModels/CurriculumViewModel.swift

@@ -42,18 +42,16 @@ extension CurriculumViewModel {
   func transform(input: Input) -> Output {
     let semesterInput = SemesterViewModel.Input(targetStudentId: input.targetStudentId)
 
-    let semesters = semesterViewModel.transform(input: semesterInput).semesters
+    let semesterOutput = semesterViewModel.transform(input: semesterInput)
 
     let courseInput = CourseViewModel.Input(year: Observable.just("108"),
                                             semester: Observable.just("1"),
                                             targetStudentId: input.targetStudentId,
                                             searchTrigger: input.searchTrigger)
     let courseOutput = courseViewModel.transform(input: courseInput)
-    let state = courseOutput.state
-    let courses = courseOutput.courses
-    return Output(state: state,
-                  semesters: semesters,
-                  courses: courses)
+    return Output(state: courseOutput.state,
+                  semesters: semesterOutput.semesters,
+                  courses: courseOutput.courses)
   }
 
 }

TAT/ViewModels/SemesterViewModel.swift

@@ -36,12 +36,36 @@ final class SemesterViewModel: NSObject, ViewModelType {
 extension SemesterViewModel {
 
   func transform(input: SemesterViewModel.Input) -> SemesterViewModel.Output {
+    let semesters = input.targetStudentId
+      .filter { $0 != "" }
+      .flatMap { [unowned self] (targetStudentId) -> Observable<[Semester]> in
+        self.generateSemesters(from: targetStudentId)
+      }
+      .share()
 
-    let semesters = input.targetStudentId.flatMap { [unowned self] (targetStudentId) -> Observable<[Semester]> in
-      return self.curriculumsUseCase.semesters(targetStudentId: targetStudentId)
-    }
+    semesters
+      .subscribe(onNext: { (semesters) in
+        if UserDefaults.standard.object(forKey: "semesters") == nil {
+          guard let semesters = try? JSONEncoder().encode(semesters) else { return }
+          UserDefaults.standard.set(semesters, forKey: "semesters")
+        }
+      }, onError: { (error) in
+        print(error)
+      })
+      .disposed(by: rx.disposeBag)
 
     return Output(semesters: semesters)
   }
 
+  private func generateSemesters(from targetStudentId: String) -> Observable<[Semester]> {
+    guard let cachedTargetStudentId = UserDefaults.standard.string(forKey: "targetStudentId"),
+      cachedTargetStudentId == targetStudentId else {
+        UserDefaults.standard.set(targetStudentId, forKey: "targetStudentId")
+        return curriculumsUseCase.semesters(targetStudentId: targetStudentId)
+    }
+    guard let cachedData = UserDefaults.standard.object(forKey: "semesters") as? Data,
+      let cachedSemesters = try? JSONDecoder().decode([Semester].self, from: cachedData)
+      else { fatalError("cannot cast to semesters") }
+    return Observable.just(cachedSemesters)
+  }
 }