Add the current image/alternateImage url for NSButton category. A little code refactoring

@@ -17,6 +17,11 @@
 #pragma mark - Image
 
 /**
+ * Get the current image URL.
+ */
+- (nullable NSURL *)sd_currentImageURL;
+
+/**
  * Set the button `image` with an `url`.
  *
  * The download is asynchronous and cached.
@@ -126,6 +131,11 @@
 #pragma mark - Alternate Image
 
 /**
+ * Get the current alternateImage URL.
+ */
+- (nullable NSURL *)sd_currentAlternateImageURL;
+
+/**
  * Set the button `alternateImage` with an `url`.
  *
  * The download is asynchronous and cached.

@@ -10,9 +10,18 @@
 
 #if SD_MAC
 
+#import "objc/runtime.h"
 #import "UIView+WebCacheOperation.h"
 #import "UIView+WebCache.h"
 
+static inline NSString * imageOperationKey() {
+    return @"NSButtonImageOperation";
+}
+
+static inline NSString * alternateImageOperationKey() {
+    return @"NSButtonAlternateImageOperation";
+}
+
 @implementation NSButton (WebCache)
 
 #pragma mark - Image
@@ -46,11 +55,13 @@
                    options:(SDWebImageOptions)options
                   progress:(nullable SDWebImageDownloaderProgressBlock)progressBlock
                  completed:(nullable SDExternalCompletionBlock)completedBlock {
+    self.sd_currentImageURL = url;
+    
     __weak typeof(self)weakSelf = self;
     [self sd_internalSetImageWithURL:url
                     placeholderImage:placeholder
                              options:options
-                        operationKey:@"NSButtonImageOperation"
+                        operationKey:imageOperationKey()
                        setImageBlock:^(NSImage * _Nullable image, NSData * _Nullable imageData) {
                            weakSelf.image = image;
                        }
@@ -89,11 +100,13 @@
                             options:(SDWebImageOptions)options
                            progress:(nullable SDWebImageDownloaderProgressBlock)progressBlock
                           completed:(nullable SDExternalCompletionBlock)completedBlock {
+    self.sd_currentAlternateImageURL = url;
+    
     __weak typeof(self)weakSelf = self;
     [self sd_internalSetImageWithURL:url
                     placeholderImage:placeholder
                              options:options
-                        operationKey:@"NSButtonAlternateImageOperation"
+                        operationKey:alternateImageOperationKey()
                        setImageBlock:^(NSImage * _Nullable image, NSData * _Nullable imageData) {
                            weakSelf.alternateImage = image;
                        }
@@ -104,11 +117,29 @@
 #pragma mark - Cancel
 
 - (void)sd_cancelCurrentImageLoad {
-    [self sd_cancelImageLoadOperationWithKey:@"NSButtonImageOperation"];
+    [self sd_cancelImageLoadOperationWithKey:imageOperationKey()];
 }
 
 - (void)sd_cancelCurrentAlternateImageLoad {
-    [self sd_cancelImageLoadOperationWithKey:@"NSButtonAlternateImageOperation"];
+    [self sd_cancelImageLoadOperationWithKey:alternateImageOperationKey()];
+}
+
+#pragma mar - Private
+
+- (NSURL *)sd_currentImageURL {
+    return objc_getAssociatedObject(self, @selector(sd_currentImageURL));
+}
+
+- (void)setSd_currentImageURL:(NSURL *)sd_currentImageURL {
+    objc_setAssociatedObject(self, @selector(sd_currentImageURL), sd_currentImageURL, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
+}
+
+- (NSURL *)sd_currentAlternateImageURL {
+    return objc_getAssociatedObject(self, @selector(sd_currentAlternateImageURL));
+}
+
+- (void)setSd_currentAlternateImageURL:(NSURL *)sd_currentAlternateImageURL {
+    objc_setAssociatedObject(self, @selector(sd_currentAlternateImageURL), sd_currentAlternateImageURL, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
 }
 
 @end

@@ -26,22 +26,30 @@ static inline NSString * backgroundImageURLKeyForState(UIControlState state) {
     return [NSString stringWithFormat:@"backgroundImage_%lu", (unsigned long)state];
 }
 
+static inline NSString * imageOperationKeyForState(UIControlState state) {
+    return [NSString stringWithFormat:@"UIButtonImageOperation%lu", (unsigned long)state];
+}
+
+static inline NSString * backgroundImageOperationKeyForState(UIControlState state) {
+    return [NSString stringWithFormat:@"UIButtonBackgroundImageOperation%lu", (unsigned long)state];
+}
+
 @implementation UIButton (WebCache)
 
 #pragma mark - Image
 
 - (nullable NSURL *)sd_currentImageURL {
-    NSURL *url = self.imageURLStorage[imageURLKeyForState(self.state)];
+    NSURL *url = self.sd_imageURLStorage[imageURLKeyForState(self.state)];
 
     if (!url) {
-        url = self.imageURLStorage[imageURLKeyForState(UIControlStateNormal)];
+        url = self.sd_imageURLStorage[imageURLKeyForState(UIControlStateNormal)];
     }
 
     return url;
 }
 
 - (nullable NSURL *)sd_imageURLForState:(UIControlState)state {
-    return self.imageURLStorage[imageURLKeyForState(state)];
+    return self.sd_imageURLStorage[imageURLKeyForState(state)];
 }
 
 - (void)sd_setImageWithURL:(nullable NSURL *)url forState:(UIControlState)state {
@@ -70,16 +78,16 @@ static inline NSString * backgroundImageURLKeyForState(UIControlState state) {
                    options:(SDWebImageOptions)options
                  completed:(nullable SDExternalCompletionBlock)completedBlock {
     if (!url) {
-        [self.imageURLStorage removeObjectForKey:imageURLKeyForState(state)];
+        [self.sd_imageURLStorage removeObjectForKey:imageURLKeyForState(state)];
     } else {
-        self.imageURLStorage[imageURLKeyForState(state)] = url;
+        self.sd_imageURLStorage[imageURLKeyForState(state)] = url;
     }
     
     __weak typeof(self)weakSelf = self;
     [self sd_internalSetImageWithURL:url
                     placeholderImage:placeholder
                              options:options
-                        operationKey:[NSString stringWithFormat:@"UIButtonImageOperation%@", @(state)]
+                        operationKey:imageOperationKeyForState(state)
                        setImageBlock:^(UIImage *image, NSData *imageData) {
                            [weakSelf setImage:image forState:state];
                        }
@@ -90,17 +98,17 @@ static inline NSString * backgroundImageURLKeyForState(UIControlState state) {
 #pragma mark - Background Image
 
 - (nullable NSURL *)sd_currentBackgroundImageURL {
-    NSURL *url = self.imageURLStorage[backgroundImageURLKeyForState(self.state)];
+    NSURL *url = self.sd_imageURLStorage[backgroundImageURLKeyForState(self.state)];
     
     if (!url) {
-        url = self.imageURLStorage[backgroundImageURLKeyForState(UIControlStateNormal)];
+        url = self.sd_imageURLStorage[backgroundImageURLKeyForState(UIControlStateNormal)];
     }
     
     return url;
 }
 
 - (nullable NSURL *)sd_backgroundImageURLForState:(UIControlState)state {
-    return self.imageURLStorage[backgroundImageURLKeyForState(state)];
+    return self.sd_imageURLStorage[backgroundImageURLKeyForState(state)];
 }
 
 - (void)sd_setBackgroundImageWithURL:(nullable NSURL *)url forState:(UIControlState)state {
@@ -129,16 +137,16 @@ static inline NSString * backgroundImageURLKeyForState(UIControlState state) {
                              options:(SDWebImageOptions)options
                            completed:(nullable SDExternalCompletionBlock)completedBlock {
     if (!url) {
-        [self.imageURLStorage removeObjectForKey:backgroundImageURLKeyForState(state)];
+        [self.sd_imageURLStorage removeObjectForKey:backgroundImageURLKeyForState(state)];
     } else {
-        self.imageURLStorage[backgroundImageURLKeyForState(state)] = url;
+        self.sd_imageURLStorage[backgroundImageURLKeyForState(state)] = url;
     }
     
     __weak typeof(self)weakSelf = self;
     [self sd_internalSetImageWithURL:url
                     placeholderImage:placeholder
                              options:options
-                        operationKey:[NSString stringWithFormat:@"UIButtonBackgroundImageOperation%@", @(state)]
+                        operationKey:backgroundImageOperationKeyForState(state)
                        setImageBlock:^(UIImage *image, NSData *imageData) {
                            [weakSelf setBackgroundImage:image forState:state];
                        }
@@ -149,14 +157,16 @@ static inline NSString * backgroundImageURLKeyForState(UIControlState state) {
 #pragma mark - Cancel
 
 - (void)sd_cancelImageLoadForState:(UIControlState)state {
-    [self sd_cancelImageLoadOperationWithKey:[NSString stringWithFormat:@"UIButtonImageOperation%@", @(state)]];
+    [self sd_cancelImageLoadOperationWithKey:imageOperationKeyForState(state)];
 }
 
 - (void)sd_cancelBackgroundImageLoadForState:(UIControlState)state {
-    [self sd_cancelImageLoadOperationWithKey:[NSString stringWithFormat:@"UIButtonBackgroundImageOperation%@", @(state)]];
+    [self sd_cancelImageLoadOperationWithKey:backgroundImageOperationKeyForState(state)];
 }
 
-- (SDStateImageURLDictionary *)imageURLStorage {
+#pragma mark - Private
+
+- (SDStateImageURLDictionary *)sd_imageURLStorage {
     SDStateImageURLDictionary *storage = objc_getAssociatedObject(self, &imageURLStorageKey);
     if (!storage) {
         storage = [NSMutableDictionary dictionary];