On Fri, 23 May 2008 09:13:50 -0400, "John Salerno" <[EMAIL PROTECTED]> wrote:
>"Bruno Desthuilliers" <[EMAIL PROTECTED]> wrote in >message news:[EMAIL PROTECTED] >> Ever heard of the "Model/View/Controller" pattern ? > >Yes, I have, but I probably don't understand it well enough yet. For >example, I don't really know what is meant by phrases like "build a model", >"the view registers itself with the model", "interations are sent to the >appropriate controller" -- I may understand them literally, but I get the >feeling that the implementation of these ideas are beyond me. I doubt that. I've done things like this. I ended up with just a Model and a View, no Controller. I assumed that meant I was being Bad - I read once that that often happens, specifically with GUI programs. An example, certainly not meant to be definitive, maybe not even right, probably not "right", but illustrating explicitly what those terms you claim not to understand might mean in an implementation: class Model: """Encapsulates an abstract version of the game: Knows nothing about how the players make moves, the moves are reported to the model via the ProcessMove method. Knows nothing about how the state of the game is displayed to the players; that's handled by the view or views. The model might contain a matrix, where the entry in each cell is None or a certain Piece object. The model knows that if a certain Cell contains a King then it's legal to move that King to this Cell but not to that Cell - that's part of the rules of the game, something the View knows nothing about""" def __init__(self): #set up internal state, for example #self.board = [[None]*8]*8 #and then self.board[0,4] = Queen[WhitePlayer], #etc. Whatever... self.views = [] #or just self.view = None if there's #no reason for multiple views. When I did #something like this once I decided at the #end that I should have allowed multiple #views even though there was only one to start, #because functionality that got added to the view #could have been done more cleanly by creating #a second view (one view being the display and #another being spoken messages) def RegisterView(self, view): self.views.append(view) #or just self.view = view def UpdateViews(self): for view in self.views: view.UpdateDisplay(self) #or UpdateView(self): if self.view: self.view.UpdateDisplay(self) def ProcessMove(self, move): """Model recieves "messages" from View here.""" #modify internal state depending on the #information passed in "move", #for example move might say that the Piece in #a certain Cell was dragged to another Cell. #Here in ProcessMove you decide whether that's #a legal move, and if so what effect it should #have on the state of the game. Update state, then self.UpdateViews() #or there could be more than one "Process" method #if there are various different sorts of things the #players might do class Square: def __init__(self, row, col): self.row = row self.col = col #say a move is a drag from one square to another: class Move: def __init__(self, start, end) self.start = start self.end = end #wrote that out explicitly just to emphasize that #the Move object, which the View passes to the #Model as a message, doesn't know anything #about the details of the display and also doesn't #know anything about the rules of the game... class View: def __init__(self, game): #set up the wxPython stuff self.game = game self.game.RegisterView(self) Bind(self, VariousEvents, VariousHandlers) def VariousHandlers(self, evt) #figure out what the players just did based #on evt. Maybe a player has just dragged a piece #from one square to another. figure out the row #and col of the start and end squares from #information in evt. #Now tell the Model what just happened: self.game.ProcessMove(Move(Square(row1, col1),Square(row2, col2))) def UpdateDisplay(self): #look at self.game to figure out what pieces #go where, then draw them on the screen. wx.This wx.That game = Model() view = View(game) >I think it's >mainly an issue of terminology, so probably I should just read up on MVC. > >> The user interface doesn't need to be graphical. There were games and >> emails clients and text editors before GUIs existed, you know ? > >Of course, but I'm specifically asking about creating a program that has a >GUI, and even more specifically it would be wxPython. > David C. Ullrich -- http://mail.python.org/mailman/listinfo/python-list
