Fixed #655

core/src/io/anuke/mindustry/world/Block.java

@@ -45,6 +45,8 @@ public class Block extends BlockStorage{
     public boolean update;
     /** whether this block has health and can be destroyed */
     public boolean destructible;
+    /** whether unloaders work on this block*/
+    public boolean unloadable = true;
     /** whether this is solid */
     public boolean solid;
     /** whether this block CAN be solid. */

core/src/io/anuke/mindustry/world/blocks/distribution/Conveyor.java

@@ -42,6 +42,7 @@ public class Conveyor extends Block{
 
         idleSound = Sounds.conveyor;
         idleSoundVolume = 0.004f;
+        unloadable = false;
     }
 
     private static int compareItems(long a, long b){

core/src/io/anuke/mindustry/world/blocks/distribution/Junction.java

@@ -26,6 +26,7 @@ public class Junction extends Block{
         solid = true;
         instantTransfer = true;
         group = BlockGroup.transportation;
+        unloadable = false;
     }
 
     @Override

core/src/io/anuke/mindustry/world/blocks/distribution/OverflowGate.java

@@ -18,6 +18,7 @@ public class OverflowGate extends Block{
         solid = true;
         update = true;
         group = BlockGroup.transportation;
+        unloadable = false;
     }
 
     @Override

core/src/io/anuke/mindustry/world/blocks/distribution/Router.java

@@ -17,6 +17,7 @@ public class Router extends Block{
         hasItems = true;
         itemCapacity = 1;
         group = BlockGroup.transportation;
+        unloadable = false;
     }
 
     @Override

core/src/io/anuke/mindustry/world/blocks/distribution/Sorter.java

@@ -26,6 +26,7 @@ public class Sorter extends Block{
         instantTransfer = true;
         group = BlockGroup.transportation;
         configurable = true;
+        unloadable = false;
     }
 
     @Override

core/src/io/anuke/mindustry/world/blocks/storage/Unloader.java

@@ -59,9 +59,9 @@ public class Unloader extends Block{
 
         if(tile.entity.timer.get(timerUnload, speed / entity.timeScale) && tile.entity.items.total() == 0){
             for(Tile other : tile.entity.proximity()){
-                if(other.interactable(tile.getTeam()) && other.block() instanceof StorageBlock && entity.items.total() == 0 &&
-                ((entity.sortItem == null && other.entity.items.total() > 0) || ((StorageBlock)other.block()).hasItem(other, entity.sortItem))){
-                    offloadNear(tile, ((StorageBlock)other.block()).removeItem(other, entity.sortItem));
+                if(other.interactable(tile.getTeam()) && other.block().unloadable && entity.items.total() == 0 &&
+                ((entity.sortItem == null && other.entity.items.total() > 0) || hasItem(other, entity.sortItem))){
+                    offloadNear(tile, removeItem(other, entity.sortItem));
                 }
             }
         }
@@ -71,6 +71,38 @@ public class Unloader extends Block{
         }
     }
 
+    /**
+     * Removes an item and returns it. If item is not null, it should return the item.
+     * Returns null if no items are there.
+     */
+    private Item removeItem(Tile tile, Item item){
+        TileEntity entity = tile.entity;
+
+        if(item == null){
+            return entity.items.take();
+        }else{
+            if(entity.items.has(item)){
+                entity.items.remove(item, 1);
+                return item;
+            }
+
+            return null;
+        }
+    }
+
+    /**
+     * Returns whether this storage block has the specified item.
+     * If the item is null, it should return whether it has ANY items.
+     */
+    private boolean hasItem(Tile tile, Item item){
+        TileEntity entity = tile.entity;
+        if(item == null){
+            return entity.items.total() > 0;
+        }else{
+            return entity.items.has(item);
+        }
+    }
+
     @Override
     public void draw(Tile tile){
         super.draw(tile);