<div dir="ltr"><br><br><div class="gmail_quote">On Thu, Oct 2, 2008 at 6:17 PM, Sean Allen <span dir="ltr"><<a href="mailto:sean@monkeysnatchbanana.com">sean@monkeysnatchbanana.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
<div style=""><div class="Ih2E3d">You'd have to specially code each accessor in that case to check the flag.</div></div></blockquote><div><br>Yes. This is unlikely to be a problem unless you have a lot of members.<br>
<br>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.<br> <br></div><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
<div style=""><div class="Ih2E3d"><div><br></div><div>Ideally I'd like to be able to step in front of every message send to descendent objects and</div><div>decide whether to pass along ( read call ) or reject ( write call ).</div>
<div><br></div><div>then, all the logic is in one place and the accessors don't need to know about what is going on.</div><div><br></div><div>any way to do that?</div><div><br></div></div><div class="Ih2E3d"><div>i'm ok with the primitive problem as i don't need real immutability. just 'application level' immutability...</div>
<div>ideally, without special coding in every accessor method ( that would get tedious very quickly ).</div><div><br></div></div><div><br><div><div class="Ih2E3d"><div>On Oct 2, 2008, at 12:47 PM, Marcin Tustin wrote:</div>
<br></div><div><div></div><div class="Wj3C7c"><blockquote type="cite"><div>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. <br>
</div> <div>Or am I missing something?<br> </div> <div><span class="gmail_quote">On 10/2/08, <b class="gmail_sendername">Randal L. Schwartz</b> <<a href="mailto:merlyn@stonehenge.com" target="_blank">merlyn@stonehenge.com</a>> wrote:</span> <blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0px 0px 0px 0.8ex; padding-left: 1ex;">
>>>>> "Sean" == Sean Allen <<a href="mailto:sean@monkeysnatchbanana.com" target="_blank">sean@monkeysnatchbanana.com</a>> writes:<br> <br>Sean> If you wanted to take a mutable object and make it immutable and be able<br>
Sean> to go back again to mutable, how could you do that?<br><br>Squeak doesn't have that sort of capability. The immutability of a few<br> classes is because the VM recognizes them specially, and not available<br>
at the programmer level without modifying the VM.<br><br>Other Smalltalk VMs are different. I think both VisualWorks and GemStone/S<br>have primitive bits on an object to be informed when a mutation might be<br> attempted.<br>
<br>You can simulate that *mostly* in Squeak by using a "proxy" object that<br>intercepts all messages and looks for the dangerous ones, but that's gonna be<br>a bit hard to do, and won't be aware of any new code that might call the<br>
mutating primitives directly. (*Any* method can call a primitive.)<br><br>--<br>Randal L. Schwartz - Stonehenge Consulting Services, Inc. - +1 503 777 0095<br><<a href="mailto:merlyn@stonehenge.com" target="_blank">merlyn@stonehenge.com</a>> <URL:<a href="http://www.stonehenge.com/merlyn/" target="_blank">http://www.stonehenge.com/merlyn/</a>><br>
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