Game sometimes not detecting collisions or something?

Here is a picture of my game:

I use a multidimensional array to place the tiles of the walls, the enemies, coins and player in their initial positions. I then use this array to determine if enemies or the player can enter a position. If the position they are wanting to move in is not a wall, then it can be made. I make use of object.transform() to change the position of the enemies & players, and update the multidimensional array to store their new positions.

I am using a non-physical collision technique in order to determine if the player has collided with an enemy or a coin. However, sometimes the game just doesn’t register the player hitting a coin. The coin just stays there, without the score going up.

Here is my code for the collision detection of the player & coins specifically:

for i = 1, #coinCache, 1 do
        -- Check for collision between player and this coin instance
        if ( coinCache[i] and hasCollidedRect( player, coinCache[i] ) ) then
            score = score + 1
            -- Remove the coin from the screen
            display.remove( coinCache[i] )
            -- Remove reference from table
            coinCache[i] = nil
            -- Handle other collision aspects like increasing score, etc.

            if score >= 10 then


And here is the function used within that code:

local function hasCollidedRect( obj1, obj2 )
    if ( obj1 == nil ) then  -- Make sure the first object exists
        return false
    if ( obj2 == nil ) then  -- Make sure the other object exists
        return false
    local left = obj1.contentBounds.xMin+1 <= obj2.contentBounds.xMin+1 and obj1.contentBounds.xMax-1 >= obj2.contentBounds.xMin+1
    local right = obj1.contentBounds.xMin+1 >= obj2.contentBounds.xMin+1 and obj1.contentBounds.xMin+1 <= obj2.contentBounds.xMax-1
    local up = obj1.contentBounds.yMin+1 <= obj2.contentBounds.yMin+1 and obj1.contentBounds.yMax-1 >= obj2.contentBounds.yMin+1
    local down = obj1.contentBounds.yMin+1 >= obj2.contentBounds.yMin+1 and obj1.contentBounds.yMin+1 <= obj2.contentBounds.yMax-1
    return ( left or right ) and ( up or down )

Any help would be appreciated.

It’s probably because you are removing a coin fro the cache upon collision and the loop you are using to iterate through the cache goes from index 1 to max so if you remove a coin on collision, the objects at higher indices probably get moved down the order and since your variable ‘i’ continues to increase, you are missing some checks in the process.

Running it as i=#coinCache,1,-1 might fix it.

I actually tried with that too, and it didn’t change a thing.

Try @famousdoggstudios advice and use table.remove( coinCache, i ) instead of coinCache[i]=nil

See Safely remove items from an array table while iterating

Thank you so much. I think this has solved my issue :slight_smile:

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