Scratch that, this won't work on UIButton

SDWebImage/UIButton+WebCache.h

@@ -14,14 +14,6 @@
  */
 @interface UIButton (WebCache)
 
-/**
- * Get the current image URL.
- *
- * Note that because of the limitations of categories this property can get out of sync
- * if you use setImage: directly.
- */
-- (NSURL *)currentImageURL;
-
 /**
  * Set the imageView `image` with an `url`.
  *

SDWebImage/UIButton+WebCache.m

@@ -9,16 +9,10 @@
 #import "UIButton+WebCache.h"
 #import "objc/runtime.h"
 
-static char imageURLKey;
 static char operationKey;
 
 @implementation UIButton (WebCache)
 
-- (NSURL *)currentImageURL;
-{
-    return objc_getAssociatedObject(self, &imageURLKey);
-}
-
 - (void)setImageWithURL:(NSURL *)url forState:(UIControlState)state
 {
     [self setImageWithURL:url forState:state placeholderImage:nil options:0 completed:nil];
@@ -43,7 +37,6 @@ static char operationKey;
 - (void)setImageWithURL:(NSURL *)url forState:(UIControlState)state placeholderImage:(UIImage *)placeholder options:(SDWebImageOptions)options completed:(SDWebImageCompletedBlock)completedBlock {
     [self cancelCurrentImageLoad];
 
-    objc_setAssociatedObject(self, &imageURLKey, url, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
     [self setImage:placeholder forState:state];
 
     if (url) {