Inventory Slot Clear Tile Left Behind

Hello! So I have a relatively simple inventory system with a display that displays different tiles I pick up. The way it works is that I store an array of the slot UI game objects, and then when I pick up a tile I find an Image game object in the slot and set the sprite to the sprite of the tile I just picked up. The way I've programmed it is that when I remove the inventory item, it subtracts its quantity, and if it's quantity value is equal to 0, it clears the title (image, quantity, and all that). I've put this updateDisplay function that will automatically shift the display of the titles to the left as tiles are cleared.

This function works wonderfully well, except for when I have more than 2 items. If item A is cleared, Item B moves over to Item A's original slot, and item C moves to Item B's slot, while still leaving behind itself in it's original slot. Something with the loop I use to find the slots and clear must be off.

Any help with figuring out the issue would be very much appreciated!

Remove Item from Inventory Code: (ignore the commented out code)

Spoiler

Code (CSharp):

1. public void removeTile(int itemID, int amount) {
2.         // Check to see if tile exists in inventory
3.         for (int i = 0; i < items.Count; i++) {
4.             if (items [i]._ID == itemID) {
5.                 // Subtract quantity
6.                 items [i]._quantity = items [i]._quantity - amount;
7.                 // Update inventory display
8.                 for (int j = 0; j < itemSlots.Length; j++) {
9.                     // Get slot script
10.                     Item_Slot slotScript = itemSlots [j].gameObject.GetComponent<Item_Slot> ();
11.  
12.                     if (slotScript.itemID == items [i]._ID) {
13.                         slotScript.itemQuantity = items[i]._quantity;
14.                     }
15.  
16.                     if (items [i]._quantity == 0) {
17.                         slotScript = itemSlots [j].gameObject.GetComponent<Item_Slot> ();
18.  
19.                         print ("Current item ID checking for: " + slotScript.itemID);
20.  
21.                         if (slotScript.itemID == items [i]._ID) {
22.                             clearItemSlot (j);
23.                             clearItemSlot (j + 1);
24.                         }
25.  
26.                         items.Remove (items [i]);
27.  
28.                         //updateDisplay ();
29.                     }
30.                     //updateDisplay ();
31.                 }
32.                 //print ("Quantity of " + items [i]._name + "is now " + items [i]._quantity);
33.                 // Delete item if it's quantiative value is 0
34.                 /*if (items[i]._quantity == 0) {
35.                     // Update inventorical display
36.                     for (int j = 0; j < itemSlots.Length; j++) {
37.                         // Get slot script
38.                         Item_Slot slotScript = itemSlots [j].gameObject.GetComponent<Item_Slot> ();
39.  
40.                         print ("Current item ID checking for: " + slotScript.itemID);
41.  
42.                         if (slotScript.itemID == items [i]._ID) {
43.                             clearItemSlot (j);
44.                             clearItemSlot (j + 1);
45.                         }
46.                     }
47.                     // Remove item
48.                     items.Remove (items [i]);
49.                 }*/
50.             }
51.         }
52.  
53.         updateDisplay ();
54.     }

clearItemSlot() function:

Spoiler

Code (CSharp):

1. public void clearItemSlot(int slotToClear) {
2.         print ("Clearing slot: " + slotToClear);
3.         Item_Slot slotScript = itemSlots [slotToClear].gameObject.GetComponent<Item_Slot> ();
4.  
5.         slotScript.itemQuantity = 0;
6.         slotScript._quantityText.text = "";
7.         slotScript.itemID = -1;
8.         slotScript._imageObject.sprite = null;
9.         slotScript._itemSprite = null;
10.  
11.         //updateDisplay ();
12.     }

updateDisplay() function

Spoiler

Code (CSharp):

1. public void updateDisplay() {
2.         for (int i = 0; i < items.Count; i++) {
3.             // Get their item script
4.             Item_Slot slotScript = itemSlots [i].gameObject.GetComponent<Item_Slot> ();
5.             // Set values
6.             slotScript.itemQuantity = items [i]._quantity;
7.             slotScript.itemID = items [i]._ID;
8.             slotScript._itemSprite = items [i]._item.GetComponent<SpriteRenderer> ().sprite;
9.         }
10.     }

 

bump

 

theres a few issues in RemoveInventory()
Line 17: is redunant from Line 10. you already have that slotscript from before no need to get the component again.

Line 23: can cause an ArrayIndexOutOfBoundsException

Line 26: this is likely the cause of your troubles. if you have ten slots and remove first slot (slot[0]), then 2nd slot will take its place (as slot[0]), but the variable "i" will be increment the next iteration of the loop, thus work on the 3rd slot (slot[1]) and skipping the 2nd slot (slot[0]). thus every time a slot is removed it skips checking the next slot

 

Thanks for taking the time to look through all that code! You've pointed me in the right direction, but how would you suggest I fix this error? I've tried moving around the

Code (CSharp):

1. items.Remove (items [i]);

line, but that doesn't really work. I'm thinking about maybe forgetting that line, and trying to re do the loop so that it works better. I appreciate your help!

 

a common rule (specifically when using Foreach or IEnumerators) is that you shouldn't change the state of collection while you are iterating through it. such as removing an element in the same loop that you are processing it. typically you'd flag the items you want to remove and only remove them in a 2nd loop after you processed them all in the 1st loop

assuming items is a List, you could try doing your processing normally (without any Remove) in the current loop and then after the outer loop finished make a "RemoveAll()" call. Interally RemoveAll will do this 2nd loop for you and figure out which items need to be removed based on the true/false expression you give it.

Code (CSharp):

1.  
2. //** Remove Tile Code **//
3.  
4. //removes all items where this statement would be true
5. // read as "remove any item with a quantity less than or equal to 0 from the items list"
6. items.RemoveAll(item=> item._quantity <=0);
7.  
8. updateDisplay();
9.