Re: [Pharo-users] lasergame question

[Ben Coman]

Roelof Wobben wrote: Nicolai Hess schreef op 1-4-2014 16:44: 2014-04-01 16:21 GMT+02:00 Roelof Wobben <r.wob...@home.nl>: Camille Teruel schreef op 1-4-2014 15:08: On 1 avr. 2014, at 14:52, Roelof Wobben <r.wob...@home.nl> wrote: Hello, Hello, Im on this page now: http://squeak.preeminent.org/tut2007/html/017.html I do not understand one thing. Where do I put the initialize "script" #initialize is not a script, it's a method. When an object is instantiated (for ex with: MyObject new) #initialize is automatically sent to it. This is the place to put your newly created object in a correct initial state. In your class, you just define a protocol named for example "initialization" where you put all the initialization-related methods. Note that protocols have no meaning, i.e. they don't change how your objects behave, they're just here to help you classify the methods of a class by concerns. So the tutorial tell you to create two methods: #initialize that is automatically called after an object has been instantiated and #initializeActiveSegments where you put some other initialization logic, that's all. When I put it on the initializeActiveSegments then initialize get not found. Sorry, I don't understand. Or must I make a seperate protocol named ActiveSegments for it. No use the same protocol "initialization" or "initialize-release" or whatever. Oke, I changed it so I have this : Laser-Game-Model with as classes:   - BlankCell   - Grid   - MirrorCell   -TargetCell BlankCell has the following protocols: - initializing-release - testing Initializing - release contains the following  methods:  - initialize  - initializeActiveSegments testing contains the following methods: isOn isOff but when I run the test-runner I see this : MessageNotUnderstood : BlankCell >> activeSegments. Roelof Then you missed the last step on http://squeak.preeminent.org/tut2007/html/016.html Select "create instance var accessors" from the second popup menu.  I also did. See this : Object subclass: #BlankCell     instanceVariableNames: 'activeSegments'     classVariableNames: ''     category: 'Laser-Game-Model' Roelof This only creates the instance variable.  I'm not clear whether are saying you performed the step shown in the second last snapshot on page 16 or not - but the evidence of the MNU would seem it didn't happen.  Now I'm going to extrapolate a lot a check whether you are thinking of 'activeSegments' in #initializeActiveSegments as a reference to the instance variable.  However it is not a reference to the variable (even if the name is the same) but actually a send of the #activeSegments message to 'self'.   Doing it like this rather than accessing the variable directly has the advantage of focusing access to the variable through a single point, which helps observability of variable access. Also, in a "live" environment like Smalltalk, when you have instances of class X in a running system, and you add an instance variable to X, all existing classes contain 'nil' for that added variable and _everywhere_ you directly access that variable in your code would need to be wrapped in a conditional.message like #ifNil: cheers -ben