Beginners October 2008

beginners@lists.squeakfoundation.org

62 participants
79 discussions

testing a String argument
by Mark Volkmann 02 Oct '08

02 Oct '08

What's the best way to set a local variable to true if an argument that is supposed to be a String isn't nil and has a size of at least 1? I know I can do this. hasContent := aString notNil and: [ aString isEmpty not ]. but it feels like I'm making this simple test too hard. --- Mark Volkmann

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Senders refresh
by Mark Volkmann 02 Oct '08

02 Oct '08

I see that when an entry in "Senders of" window changes so it is no longer a sender, that entry gets a line through it to indicate that. Is there a way to tell that window to refresh itself to eliminate those entries? --- Mark Volkmann

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Re: [Newbies] 'locking' an object
by Marcin Tustin 02 Oct '08

02 Oct '08

Surely if you have a wrapper class which only holds a reference to a single object that has all of the data, and that has accessors, then the wrapper can only use the accessors? The data object could have a flag that causes all of the accessors to throw an exception when it is set. Or am I missing something? On 10/2/08, Randal L. Schwartz <merlyn(a)stonehenge.com> wrote: > > >>>>> "Sean" == Sean Allen <sean(a)monkeysnatchbanana.com> writes: > > Sean> If you wanted to take a mutable object and make it immutable and be > able > Sean> to go back again to mutable, how could you do that? > > Squeak doesn't have that sort of capability. The immutability of a few > classes is because the VM recognizes them specially, and not available > at the programmer level without modifying the VM. > > Other Smalltalk VMs are different. I think both VisualWorks and GemStone/S > have primitive bits on an object to be informed when a mutation might be > attempted. > > You can simulate that *mostly* in Squeak by using a "proxy" object that > intercepts all messages and looks for the dangerous ones, but that's gonna > be > a bit hard to do, and won't be aware of any new code that might call the > mutating primitives directly. (*Any* method can call a primitive.) > > -- > Randal L. Schwartz - Stonehenge Consulting Services, Inc. - +1 503 777 0095 > <merlyn(a)stonehenge.com> <URL:http://www.stonehenge.com/merlyn/> > Smalltalk/Perl/Unix consulting, Technical writing, Comedy, etc. etc. > See http://methodsandmessages.vox.com/ for Smalltalk and Seaside > discussion > _______________________________________________ > Beginners mailing list > Beginners(a)lists.squeakfoundation.org > http://lists.squeakfoundation.org/mailman/listinfo/beginners >

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Re: [Newbies] 'locking' an object
by Marcin Tustin 02 Oct '08

02 Oct '08

On Thu, Oct 2, 2008 at 6:17 PM, Sean Allen <sean(a)monkeysnatchbanana.com>wrote: > You'd have to specially code each accessor in that case to check the flag. > Yes. This is unlikely to be a problem unless you have a lot of members. Alternatively you could adapt the code that generates your accessors to put in that check, or you could use/adapt magritte to generate your objects. > > Ideally I'd like to be able to step in front of every message send to > descendent objects and > decide whether to pass along ( read call ) or reject ( write call ). > > then, all the logic is in one place and the accessors don't need to know > about what is going on. > > any way to do that? > > i'm ok with the primitive problem as i don't need real immutability. just > 'application level' immutability... > ideally, without special coding in every accessor method ( that would get > tedious very quickly ). > > > On Oct 2, 2008, at 12:47 PM, Marcin Tustin wrote: > > Surely if you have a wrapper class which only holds a reference to a single > object that has all of the data, and that has accessors, then the wrapper > can only use the accessors? The data object could have a flag that causes > all of the accessors to throw an exception when it is set. > > Or am I missing something? > > On 10/2/08, Randal L. Schwartz <merlyn(a)stonehenge.com> wrote: >> >> >>>>> "Sean" == Sean Allen <sean(a)monkeysnatchbanana.com> writes: >> >> Sean> If you wanted to take a mutable object and make it immutable and be >> able >> Sean> to go back again to mutable, how could you do that? >> >> Squeak doesn't have that sort of capability. The immutability of a few >> classes is because the VM recognizes them specially, and not available >> at the programmer level without modifying the VM. >> >> Other Smalltalk VMs are different. I think both VisualWorks and >> GemStone/S >> have primitive bits on an object to be informed when a mutation might be >> attempted. >> >> You can simulate that *mostly* in Squeak by using a "proxy" object that >> intercepts all messages and looks for the dangerous ones, but that's gonna >> be >> a bit hard to do, and won't be aware of any new code that might call the >> mutating primitives directly. (*Any* method can call a primitive.) >> >> -- >> Randal L. Schwartz - Stonehenge Consulting Services, Inc. - +1 503 777 >> 0095 >> <merlyn(a)stonehenge.com> <URL:http://www.stonehenge.com/merlyn/> >> Smalltalk/Perl/Unix consulting, Technical writing, Comedy, etc. etc. >> See http://methodsandmessages.vox.com/ for Smalltalk and Seaside >> discussion >> _______________________________________________ >> 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 > > > > _______________________________________________ > Beginners mailing list > Beginners(a)lists.squeakfoundation.org > http://lists.squeakfoundation.org/mailman/listinfo/beginners > >

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Retrieve resources via HTTP alongside with the server's http parameters
by Lothar Kaiser 02 Oct '08

02 Oct '08

Hi fellow-squeakers, I was wondering how to retrieve content from a webserver (e.g. an image) togehter with the server's http response parameters. When I use HTTPClient/HTTPSocket I only get the MimeDocument containing the content specified by the URL, additional response parameters are dropped. Is there an elegant way to get the content and all HTTP response parameters in the same go? Since the content can be quite large, I need to do the GET request only once.. Until now I ripped and modified HTTPSocket class >> #httpGetDocument: url args: args accept: mimeType request: requestString ,but this is a rather dirty way of doing it. Any ideas? cheers, Lothar

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capturing output in memory
by Mark Volkmann 02 Oct '08

02 Oct '08

For the purpose of writing unit tests for code that writes to a stream I want to use something other than a FileStream that will allow me to write to it just like FileStream, but will just hold the data in memory. When I'm finished writing, I want to retrieve everything I've written as a single String. Is there a class that does that? --- Mark Volkmann

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Failing to install IRCe
by Andy Burnett 01 Oct '08

01 Oct '08

I thought I would try using the IRC channel, so I used the package browser to install the package. Unfortunately, I get a walk back window in which the system is complaining about "unable to find function address" and gives error code 13. I am running OSX 10.5.4 Firefox 3.0.3 Squeak 3.8.18beta3U Image: squeak3.10.2-7179-basic.image. The failed external call seems to be: "which firefox" Does anyone have any thoughts on how to fix this? Cheers AB

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exception handling lingo
by Mark Volkmann 01 Oct '08

01 Oct '08

I asked this earlier, but it wasn't the first question in my email, so it may have been overlooked. 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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TODO comments and searching
by Mark Volkmann 01 Oct '08

01 Oct '08

If I put TODO comments in my code to mark things I still need to finish, is there an easy way to get a list of all of those? For that matter, how do you search all the code in a given category for a given string? --- Mark Volkmann

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Beginners October 2008