Question

I have some trouble finding appropriate patterns for what I want to do.

I have a block game with two game modes. In one mode, any removed blocks are replaced by new blocks dropped from the top of the screen. In the other mode, removed blocks are replaced by a complete new row of blocks rising from the bottom and pushing the whole field up. So I thought it would be best to use the Strategy pattern to implement this.

Now the problem is, that this Strategy would need modifying access to all the positions of existing blocks in the playing field, but obviously that information lies within the Strategy’s user class (the Game class) and I can’t have circular dependencies.

I could pass the whole field as a reference, but I have the additional problem that all the Block generation code lies within the Game class (as it should in my opinion). So the only thing that comes to mind is pass all these methods as function references, but to me that seems like overkill.

So any way to resolve this? Maybe I’m on the wrong track by wanting to use the Strategy Pattern. Help is greatly appreciated.

Bonus points for any hints regarding the use of two Strategy Pattern objects in a class that need access to the same methods which depend on members in the user class.

I’m coding in Java if that is of help

Answer 1

I guess in the end it was kind of too complex to assume an out-of-the-box answer.

I kind of followed Traxdata’s hint of decoupling more together with Mister Smith’s suggestion to actually pass references to other objects.

My final solution consists of having a FieldManager, a Field and a Strategy class. The FieldManager contains a Field and Strategy instance. The Field class contains the block creation code.

So whenever blocks need to be created or removed, the appropriate function calls the corresponding Strategy’s function and passes a reference to the field. So whenever a Strategy needs to create or remove something in the field it can do so via the field object.