Add image fading duration property.

Distrib/MoaDistrib.swift

@@ -50,6 +50,11 @@ The class can be instantiated and used without an image view:
 public final class Moa {
   private var imageDownloader: MoaImageDownloader?
   private weak var imageView: MoaImageView?
+  /// Image download did start at this time.
+  private var imageDownloadStart: Date?
+
+  /// If the request finishes before this time, changes are not animated (e.g. by fading).
+  private static let animateChangeLimit: TimeInterval = 0.1
 
   /// Image download settings.
   public static var settings = MoaSettings() {
@@ -117,6 +122,7 @@ public final class Moa {
   public func cancel() {
     imageDownloader?.cancel()
     imageDownloader = nil
+    imageDownloadStart = nil
   }
 
   /**
@@ -192,19 +198,30 @@ public final class Moa {
   */
   public static var errorImage: MoaImage?
 
+  #if os(iOS) || os(tvOS)
+  /// Set a value greater than zero to make Moa fade in the image over the given time after downloading it from the network.
+  public var imageFadeDuration: TimeInterval?
+
+  /// Set a value greater than zero to make Moa fade in images over the given time after downloading them from the network.
+  public static var imageFadeDuration: TimeInterval?
+  #endif
+
   private func startDownload(_ url: String) {
     cancel()
 
     let simulatedDownloader = MoaSimulator.createDownloader(url)
     imageDownloader = simulatedDownloader ?? MoaHttpImageDownloader(logger: Moa.logger)
     let simulated = simulatedDownloader != nil
-
+
+    imageDownloadStart = Date()
+
     imageDownloader?.startDownload(url,
       onSuccess: { [weak self] image in
         self?.handleSuccessAsync(image, isSimulated: simulated)
       },
       onError: { [weak self] error, response in
         self?.handleErrorAsync(error, response: response, isSimulated: simulated)
+        self?.imageDownloadStart = nil
       }
     )
   }
@@ -247,9 +264,47 @@ public final class Moa {
     if let onSuccess = onSuccess, let image = image {
       imageForView = onSuccess(image)
     }
-
+
+    #if os(iOS) || os(tvOS)
+    if
+      let imageView = self.imageView,
+      imageView.image != imageForView,
+      let imageFadeDuration = self.shouldFadeWithDuration()
+    {
+      UIView.transition(
+        with: imageView,
+        duration: imageFadeDuration,
+        options: .transitionCrossDissolve,
+        animations: { imageView.image = imageForView }
+      )
+    } else {
+      imageView?.image = imageForView
+    }
+    #else
     imageView?.image = imageForView
+    #endif
+
+    self.imageDownloadStart = nil
+  }
+
+  #if os(iOS) || os(tvOS)
+  /// A fade duration that is greater than zero. Only provided when the download time surpasses animateChangeLimit.
+  private func shouldFadeWithDuration() -> TimeInterval? {
+
+    let downloadTime: TimeInterval = imageDownloadStart.map { Date().timeIntervalSince($0) } ?? .zero
+    guard downloadTime > Moa.animateChangeLimit else {
+      return nil
+    }
+
+    if let duration = self.imageFadeDuration, duration > 0 {
+      return duration
+    }
+    if let duration = Moa.imageFadeDuration, duration > 0 {
+      return duration
+    }
+    return nil
   }
+  #endif
 
   /**
 

Moa/Moa.swift

@@ -35,6 +35,11 @@ The class can be instantiated and used without an image view:
 public final class Moa {
   private var imageDownloader: MoaImageDownloader?
   private weak var imageView: MoaImageView?
+  /// Image download did start at this time.
+  private var imageDownloadStart: Date?
+
+  /// If the request finishes before this time, changes are not animated (e.g. by fading).
+  private static let animateChangeLimit: TimeInterval = 0.1
 
   /// Image download settings.
   public static var settings = MoaSettings() {
@@ -102,6 +107,7 @@ public final class Moa {
   public func cancel() {
     imageDownloader?.cancel()
     imageDownloader = nil
+    imageDownloadStart = nil
   }
 
   /**
@@ -177,19 +183,30 @@ public final class Moa {
   */
   public static var errorImage: MoaImage?
 
+  #if os(iOS) || os(tvOS)
+  /// Set a value greater than zero to make Moa fade in the image over the given time after downloading it from the network.
+  public var imageFadeDuration: TimeInterval?
+
+  /// Set a value greater than zero to make Moa fade in images over the given time after downloading them from the network.
+  public static var imageFadeDuration: TimeInterval?
+  #endif
+
   private func startDownload(_ url: String) {
     cancel()
 
     let simulatedDownloader = MoaSimulator.createDownloader(url)
     imageDownloader = simulatedDownloader ?? MoaHttpImageDownloader(logger: Moa.logger)
     let simulated = simulatedDownloader != nil
-
+
+    imageDownloadStart = Date()
+
     imageDownloader?.startDownload(url,
       onSuccess: { [weak self] image in
         self?.handleSuccessAsync(image, isSimulated: simulated)
       },
       onError: { [weak self] error, response in
         self?.handleErrorAsync(error, response: response, isSimulated: simulated)
+        self?.imageDownloadStart = nil
       }
     )
   }
@@ -232,9 +249,47 @@ public final class Moa {
     if let onSuccess = onSuccess, let image = image {
       imageForView = onSuccess(image)
     }
-
+
+    #if os(iOS) || os(tvOS)
+    if
+      let imageView = self.imageView,
+      imageView.image != imageForView,
+      let imageFadeDuration = self.shouldFadeWithDuration()
+    {
+      UIView.transition(
+        with: imageView,
+        duration: imageFadeDuration,
+        options: .transitionCrossDissolve,
+        animations: { imageView.image = imageForView }
+      )
+    } else {
+      imageView?.image = imageForView
+    }
+    #else
     imageView?.image = imageForView
+    #endif
+
+    self.imageDownloadStart = nil
+  }
+
+  #if os(iOS) || os(tvOS)
+  /// A fade duration that is greater than zero. Only provided when the download time surpasses animateChangeLimit.
+  private func shouldFadeWithDuration() -> TimeInterval? {
+
+    let downloadTime: TimeInterval = imageDownloadStart.map { Date().timeIntervalSince($0) } ?? .zero
+    guard downloadTime > Moa.animateChangeLimit else {
+      return nil
+    }
+
+    if let duration = self.imageFadeDuration, duration > 0 {
+      return duration
+    }
+    if let duration = Moa.imageFadeDuration, duration > 0 {
+      return duration
+    }
+    return nil
   }
+  #endif
 
   /**
 

MoaTests/Utils/MoaTimeTests.swift

@@ -4,7 +4,8 @@ import XCTest
 
 class MoaTimeTests: XCTestCase {
   func testLogTimeDate() {
-    let calendar = Calendar.current
+    var calendar = Calendar.current
+    calendar.timeZone = TimeZone(secondsFromGMT: 0)!
     let components = NSDateComponents()
     components.year = 2027
     components.month = 11
@@ -17,6 +18,6 @@ class MoaTimeTests: XCTestCase {
 
     let result = MoaTime.logTime(date)
 
-    XCTAssertEqual("2027-11-21 02:51:41.000", result)
+    XCTAssertEqual("2027-11-21 13:51:41.000", result)
   }
 }

moa.podspec

@@ -1,8 +1,8 @@
 Pod::Spec.new do |s|
   s.name        = "moa"
-  s.version     = "12.0.0"
+  s.version     = "12.1.0"
   s.license     = { :type => "MIT" }
-  s.homepage    = "https://github.com/evgenyneu/moa"
+  s.homepage    = "https://github.com/r-dent/moa"
   s.summary     = "An image download extension for image view written in Swift."
   s.description  = <<-DESC
                    Moa is an image download library written in Swift for iOS, tvOS and macOS.
@@ -16,8 +16,8 @@ Pod::Spec.new do |s|
                    * Includes unit testing mode for faking network responses.
                    DESC
   s.authors     = { "Evgenii Neumerzhitckii" => "sausageskin@gmail.com" }
-  s.source      = { :git => "https://github.com/evgenyneu/moa.git", :tag => s.version }
-  s.screenshots  = "https://raw.githubusercontent.com/evgenyneu/moa/master/Graphics/Hunting_Moa.jpg"
+  s.source      = { :git => "https://github.com/r-dent/moa.git", :tag => s.version }
+  s.screenshots  = "https://raw.githubusercontent.com/r-dent/moa/master/Graphics/Hunting_Moa.jpg"
   s.source_files = "Moa/**/*.swift"
   s.ios.deployment_target = "8.0"
   s.osx.deployment_target = "10.9"