From e7a920b8d06f1aaf0f86826e862bb5fced909356 Mon Sep 17 00:00:00 2001
From: Glenn Posadas <hello@glennvon.com>
Date: Thu, 15 Apr 2021 03:25:03 +0800
Subject: [PATCH] fix image loading

---
 .../Screens/Search/MovieTableViewCell.swift   | 31 ++++++-------------
 .../ImageLoader/ImageLoaderService.swift      | 20 ++++++------
 .../ImageLoader/ImageLoaderServiceType.swift  |  2 +-
 TMDB/Sources/UseCases/MoviesUseCase.swift     | 25 ++++++++-------
 4 files changed, 35 insertions(+), 43 deletions(-)

diff --git a/TMDB/Sources/Screens/Search/MovieTableViewCell.swift b/TMDB/Sources/Screens/Search/MovieTableViewCell.swift
index ab160e4..82de7e6 100644
--- a/TMDB/Sources/Screens/Search/MovieTableViewCell.swift
+++ b/TMDB/Sources/Screens/Search/MovieTableViewCell.swift
@@ -17,32 +17,19 @@ class MovieTableViewCell: UITableViewCell, NibProvidable, ReusableView {
     @IBOutlet private var poster: UIImageView!
     private var cancellable: AnyCancellable?
 
-    override func prepareForReuse() {
-        super.prepareForReuse()
-        cancelImageLoading()
-    }
-
     func bind(to viewModel: MovieViewModel) {
         cancelImageLoading()
         title.text = viewModel.title
         subtitle.text = viewModel.subtitle
         rating.text = viewModel.rating
-        cancellable = viewModel.poster.sink { [unowned self] image in self.showImage(image: image) }
+      
+        cancellable = viewModel.poster
+          .receive(on: DispatchQueue.main)
+          .assign(to: \.poster.image, on: self)
     }
-
-    private func showImage(image: UIImage?) {
-        cancelImageLoading()
-        UIView.transition(with: self.poster,
-        duration: 0.3,
-        options: [.curveEaseOut, .transitionCrossDissolve],
-        animations: {
-            self.poster.image = image
-        })
-    }
-
-    private func cancelImageLoading() {
-        poster.image = nil
-        cancellable?.cancel()
-    }
-
+  
+  private func cancelImageLoading() {
+      poster.image = nil
+      cancellable?.cancel()
+  }
 }
diff --git a/TMDB/Sources/Services/ImageLoader/ImageLoaderService.swift b/TMDB/Sources/Services/ImageLoader/ImageLoaderService.swift
index 8da9a30..30c32b8 100644
--- a/TMDB/Sources/Services/ImageLoader/ImageLoaderService.swift
+++ b/TMDB/Sources/Services/ImageLoader/ImageLoaderService.swift
@@ -11,21 +11,23 @@ import UIKit.UIImage
 import Combine
 
 final class ImageLoaderService: ImageLoaderServiceType {
-
+    
     private let cache: ImageCacheType = ImageCache()
-
-    func loadImage(from url: URL) -> AnyPublisher<UIImage?, Never> {
+    
+    func loadImage(from url: URL, placeholder: UIImage? = nil) -> AnyPublisher<UIImage?, Never> {
         if let image = cache.image(for: url) {
             return .just(image)
         }
         return URLSession.shared.dataTaskPublisher(for: url)
-            .map { (data, response) -> UIImage? in return UIImage(data: data) }
-            .catch { error in return Just(nil) }
-            .handleEvents(receiveOutput: {[unowned self] image in
-                guard let image = image else { return }
+            .tryMap { data, response -> UIImage in
+                guard let image = UIImage(data: data) else {
+                    throw NSError(domain: "", code: 1, userInfo: nil)
+                }
+                
                 self.cache.insertImage(image, for: url)
-            })
-            .print("Image loading \(url):")
+                return image
+            }
+            .replaceError(with: placeholder)
             .eraseToAnyPublisher()
     }
 }
diff --git a/TMDB/Sources/Services/ImageLoader/ImageLoaderServiceType.swift b/TMDB/Sources/Services/ImageLoader/ImageLoaderServiceType.swift
index 51c1e02..07e7bf8 100644
--- a/TMDB/Sources/Services/ImageLoader/ImageLoaderServiceType.swift
+++ b/TMDB/Sources/Services/ImageLoader/ImageLoaderServiceType.swift
@@ -11,5 +11,5 @@ import UIKit.UIImage
 import Combine
 
 protocol ImageLoaderServiceType: AnyObject, AutoMockable {
-    func loadImage(from url: URL) -> AnyPublisher<UIImage?, Never>
+    func loadImage(from url: URL, placeholder: UIImage?) -> AnyPublisher<UIImage?, Never>
 }
diff --git a/TMDB/Sources/UseCases/MoviesUseCase.swift b/TMDB/Sources/UseCases/MoviesUseCase.swift
index 3cfc2c5..c49773e 100644
--- a/TMDB/Sources/UseCases/MoviesUseCase.swift
+++ b/TMDB/Sources/UseCases/MoviesUseCase.swift
@@ -53,16 +53,19 @@ final class MoviesUseCase: MoviesUseCaseType {
     }
 
     func loadImage(for movie: Movie, size: ImageSize) -> AnyPublisher<UIImage?, Never> {
-        return Deferred { return Just(movie.poster) }
-        .flatMap({[unowned self] poster -> AnyPublisher<UIImage?, Never> in
-            guard let poster = movie.poster else { return .just(nil) }
-            let url = size.url.appendingPathComponent(poster)
-            return self.imageLoaderService.loadImage(from: url)
-        })
-        .subscribe(on: Scheduler.backgroundWorkScheduler)
-        .receive(on: Scheduler.mainScheduler)
-        .share()
-        .eraseToAnyPublisher()
+        guard let poster = movie.poster else { return .just(nil) }
+        let url = size.url.appendingPathComponent(poster)
+        return imageLoaderService.loadImage(from: url, placeholder: imageFrom(color: .gray))
+    }
+    
+    func imageFrom(color: UIColor) -> UIImage {
+        let rect = CGRect(x: 0, y: 0, width: 1, height: 1)
+        UIGraphicsBeginImageContext(rect.size)
+        let context = UIGraphicsGetCurrentContext()
+        context!.setFillColor(color.cgColor)
+        context!.fill(rect)
+        let img = UIGraphicsGetImageFromCurrentImageContext()
+        UIGraphicsEndImageContext()
+        return img!
     }
-
 }