Beginners September 2008

beginners@lists.squeakfoundation.org

56 participants
87 discussions

Base64 conversion for images
by Matthias Korn 30 Sep '08

30 Sep '08

Hi, I want to transfer thumbnails as one part of some more structured data via XML. I thought about embedding the thumbs encoded in Base64 directly into the XML file rather than transferring them separately. How can I decode the string from within the XML file to use and display the thumbs in Squeak (they are either gif, jpg or png). I had a look at Base64MimeConverter but couldn't quite figure it out Another use case is converting thumbs on my hard drive to a Base64 string (i.e. encoding...). From a FileStream..? I guess Base64MimeConverter is the right thing. Is there some documentation on how to use it? Thanks, matsch

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who signals?
by Mark Volkmann 29 Sep '08

29 Sep '08

Is there an easy way to get a list of all the methods hat signal a given exception class? In Smalltalk lingo is it correct to say "signal" and "handle" in place of Java's "throw" and "catch"? --- Mark Volkmann

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URI validation
by Mark Volkmann 29 Sep '08

29 Sep '08

Is there a provide class that can determine whether a given string is a valid URI? --- Mark Volkmann

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Re: [Newbies] constants
by Marcin Tustin 29 Sep '08

29 Sep '08

A class is "just" another object whose own class is Class. I actually don't know when the class initialisiation method is called after creation. As usual, if all it does is things you know to be safe, go ahead and call it manually. On 9/29/08, Mark Volkmann <mark(a)ociweb.com> wrote: > > On Sep 29, 2008, at 6:00 AM, Marcin Tustin wrote: > > The initialize method on the class side will be called only when *the > class* is initialised. You are thinking of the instance-side initialize > method which is called each time you create an instance. > > > > Wow. I wasn't aware that there was both a class and instance initialize > method. Thanks for explaining that! > > > What causes the class initialize method to be invoked ... and reinvoked > after I change it? > > On 9/29/08, Mark Volkmann <mark(a)ociweb.com> wrote: >> >> On Sep 28, 2008, at 11:32 PM, K. K. Subramaniam wrote: >> >> On Sunday 28 Sep 2008 7:26:43 pm Mark Volkmann wrote: >>> >>>> I think my main issue is scoping. I want to define a constant that is >>>> associated with a class to avoid name conflicts. >>>> >>> See classes Color, Cursor or Float for examples of scoped constants: >>> Color red >>> Cursor wait >>> Float pi >>> >>> For constants that should be exposed to a few (but not all) classes, use >>> pool >>> dictionaries. >>> >> >> Thanks! This brings up another question. Where is a good place to >> initialize a constant? I see in the case of "Float pi" that it is held in a >> class variable that is initialized in the initialize method. Isn't it the >> case that the initialize method is only called if a Float object is created? >> Also, isn't it called every time a Float object is created? It seems that >> would mean if I followed that pattern for one of my own constants then I >> wouldn't be sure it was set and I'd pay the cost of setting it many times. >> >> --- >> Mark Volkmann >> >> >> >> >> _______________________________________________ >> Beginners mailing list >> Beginners(a)lists.squeakfoundation.org >> http://lists.squeakfoundation.org/mailman/listinfo/beginners >> > > _______________________________________________ > Beginners mailing list > Beginners(a)lists.squeakfoundation.org > http://lists.squeakfoundation.org/mailman/listinfo/beginners > > > > --- > Mark Volkmann > > > > > > > > > _______________________________________________ > Beginners mailing list > Beginners(a)lists.squeakfoundation.org > http://lists.squeakfoundation.org/mailman/listinfo/beginners > >

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changing fonts
by Mark Volkmann 29 Sep '08

29 Sep '08

I'd like to try a different font, at least for the edit pane in the browser. When I select appearance...system fonts...default text font from the World menu, I see fonts from Accuat to ComicSansMS ... only 13 fonts. How do I get to fonts after ComicSansMS? --- Mark Volkmann

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Re: [Newbies] constants
by Marcin Tustin 29 Sep '08

29 Sep '08

The initialize method on the class side will be called only when *the class* is initialised. You are thinking of the instance-side initialize method which is called each time you create an instance. On 9/29/08, Mark Volkmann <mark(a)ociweb.com> wrote: > > On Sep 28, 2008, at 11:32 PM, K. K. Subramaniam wrote: > > On Sunday 28 Sep 2008 7:26:43 pm Mark Volkmann wrote: >> >>> I think my main issue is scoping. I want to define a constant that is >>> associated with a class to avoid name conflicts. >>> >> See classes Color, Cursor or Float for examples of scoped constants: >> Color red >> Cursor wait >> Float pi >> >> For constants that should be exposed to a few (but not all) classes, use >> pool >> dictionaries. >> > > Thanks! This brings up another question. Where is a good place to > initialize a constant? I see in the case of "Float pi" that it is held in a > class variable that is initialized in the initialize method. Isn't it the > case that the initialize method is only called if a Float object is created? > Also, isn't it called every time a Float object is created? It seems that > would mean if I followed that pattern for one of my own constants then I > wouldn't be sure it was set and I'd pay the cost of setting it many times. > > --- > Mark Volkmann > > > > > _______________________________________________ > Beginners mailing list > Beginners(a)lists.squeakfoundation.org > http://lists.squeakfoundation.org/mailman/listinfo/beginners >

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constants
by Mark Volkmann 29 Sep '08

29 Sep '08

How are constants represented in Smalltalk? Do you create a method whose name is the name of the constant and return the value? --- Mark Volkmann

3 5

Are setters a good idea?
by Andy Burnett 29 Sep '08

29 Sep '08

I read somewhere - can't remember where - that setters are considered evil. The argument was that in the real world you can't suddenly change the colour of a car, just by settings its colour value. Instead, you have to perform some action, e.g. sprayPaintCar: aColour. Therefore in the OO world, one should tackle problems in the same way, i.e. if you want to change the value of an instance variable, you have to call some sort of action method, that makes sense in the context of the object. Without wishing to send startHolyWar to BeginnersList, do any of the experienced developers work this way, or is it just a theoretical position? cheers AB

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Re: Removing 'dead' instances
by Andy Burnett 29 Sep '08

29 Sep '08

<<< Randal said... Setting "each" to "nil" there does nothing, since you aren't updating the object that was originally in "each". >>> << Marcus said... This is a pretty common misconception. It seems to come up once a month. I wonder why - mostly it's not people who are new to programming, who I would expect to be unfamiliar with the distinction between an object or value and the location it is stored in.>> I was wondering exactly that myself. After my 'doh!' moment, when Randal explained what I was doing wrong, I was trying to work out why I had made the mistake. The conclusion I came to was that I was becoming so used to sending messages to objects, that I had confused myself into thinking that I was somehow sending 'become nil' to the object stored in :each. Cheers AB

2 1

dev image OB Package Browser
by Mark Volkmann 29 Sep '08

29 Sep '08

I'm using the OB Package Browser in the latest dev image. Is there a way to turn off the feature that outputs matching quotes as you type? It's driving me crazy because it often adds quotes where they don't belong. --- Mark Volkmann

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Beginners September 2008