How do I check if object is next to another object

One way to solve this is by using invisible sprites which overlap, but I'd like a bit more cleaner approach, without using object families and such. Array is also an option, but that would be quite a mess in my situation.

Basically I want a sprite to check if it has a specific object to the right, left, etc. For example platform behaviour can check if its by wall or not, I want to do this to a specific object/sprite.

Check if distance between objects is below a threshold and then see if the x is > or < than current object?

You can do what Somebody said, or use line of sight too.

OK, I admit at this point I am confused.

I have 2 instances of object A, and like 50 instances of object B.

If object A has variable set "active", I want it to check if its next to object B.

I did it your way now, like this:

Object B is checked (applies to all object B-s) if any object A is at given distance(s), if it is then apply animation to object B and change variable on object A.

Nothing happens.

In that, object A is only concluded in expression, does the order chain still apply in that case?

How about On collision at offset?