Worm Game: move() and grow(), please help.

[Diego Ciccia]

Hi,

I'm having problems with week 12 exercise 49 WormGame.

I don't understand how grow() and move() are supposed to talk to each other, or how grow() is supposed to grow the worm by one piece but not add the piece to the List until move() is called.  I created a variable to store a new piece when grow() is called and then add it to the list when move() is called but I don't think that is right.  The example shows that nothing is supposed to happen when grow() is called until move() is called but how can that be?  The example also shows that the first piece of the game doesn't get deleted after grow() and move() are called:

[(5,5)] // new Worm(5,5, RIGHT)
[(5,5), (6,5)] // move
[(5,5), (6,5), (7,5)] // move
[(6,5), (7,5), (8,5)] // move
[(6,5), (7,5), (8,5)] // grow
[(6,5), (7,5), (8,5), (9,5)] // move

How come (6,5) stays in the worm? Shouldn't the worm be (7, 5), (8, 5), (9, 5), (10, 5) if the first piece should be deleted?

Please help, I don't think I am understanding how these methods should be working.  Thank you!

The link to my work is here: PASTE TMC PASTEBIN LINK HERE

https://tmc.mooc.fi/mooc/paste/rtQiwAujJQcJ9zGxsdsL3A

Best regards

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[Diego Ciccia]

I believe I have solved this myself.  However, is it okay for us to create new private variables in the class Worm? I know in the past, some tests have failed because we couldn't create extra variables.  In my example, I used a variable as a flag when grow() is called.

Code:  https://tmc.mooc.fi/mooc/paste/M-ibK326q5XKQuxCN9qsVw

[ljleppan]

Hi Diego,

As far as I recall, the tests allow you to create new variables in the worm if you feel that you need that.

As for your original question, consider it like this: when ever we move, we only want the head to move by one space on the board. For that reason, we want to add the new piece to the end so the tail "stays still". The other option would be for the head to jump two spaces ahead which would look weird and be somewhat unpredictable for the player.

Hopefully that made some sense. If you want me to clear up some other things, please don't hesitate to ask :)

-Leo