Question

As a project over summer while I have some downtime from Uni I am going to build a monopoly game. This question is more about the general idea of the problem however, rather than the specific task I’m trying to carry out.

I decided to build this with a bottom up approach, creating just movement around a forty space board and then moving on to interaction with spaces. I realised that I was quite unsure of the best way of proceeding with this and I am torn between two design ideas:

1. Giving every space its own object, all sub-classes of a Space object so the interaction can be defined by the space object itself. I could do this by implementing different land() methods for each type of space.

2. Only giving the Properties and Utilities (as each property has unique features) objects and creating methods for dealing with the buying/renting etc in the main class of the program (or Board as I’m calling it). Spaces like go and super tax could be implemented by a small set of conditionals checking to see if player is on a special space.

Option 1 is obviously the OO (and I feel the correct) way of doing things but I’d like to only have to handle user interaction from the programs main class. In other words, I don’t want the space objects to be interacting with the player.
Why? Errr. A lot of the coding I’ve done thus far has had this simplicity but I’m not sure if this is a pipe dream or not for larger projects. Should I really be handling user interaction in an entirely separate class?

As you can see I am quite confused about this situation. Is there some way round this? And, does anyone have any advice on practical OO design that could help in general?

EDIT: Just like to note that I feel I lost a little focus on this question. I am interested in the general methodology of combining OO and any external action(command line, networking, GUI, file management etc) really.

Answer 1

In the end, it is up to you. That is the beauty of OO, in that it is subject to interpretation. There are some patterns that should usually be adhered to, but in general it is your decision how to approach it.

However, you should carefully consider what each actor in the system should know about the rest of it. Should a property really know about the player, his account balance, and the other players? Probably not. A property should know what it costs, how much its rent is, etc.

On the other hand, should the main playing thread be concerned about trivial matters such as paying rent? Probably not. Its main concern should be the state of the game itself, such as dice rolling, whether each player wants to trade or buy or unmortgage/mortgage, things like that.

Think for a moment about the action of landing on a square. Once landed, the player has 3 options:

• Buy the property
• Ignore the property
• Pay rent

Now, which actor in the system knows all the information required to complete that. We have the Game class, which isn’t concerned with such tedium. We have the Property, which doesn’t really care about the players. But the Player object knows all this information. It keeps a record of what each player owns, and can easily access the proper data.

So, if it were me, I would make a Player.performMove(Die d) method. It has easy access to the accounts. This also allows for the least coupling among classes.

But in the end, it’s up to you. I’m sure people have created Monopoly clones in perfect OO, as well as Functional or Procedural languages too. In the end, use what you know and keep refactoring until you’re happy with the end design.