<br><br><div><span class="gmail_quote">On 9/28/07, <b class="gmail_sendername">Alejandro Martínez</b> <<a href="mailto:alemartinez2112@gmail.com">alemartinez2112@gmail.com</a>> wrote:</span><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
I was thinking about implementing a Proxy but instead the usual way which I believe is subclassing from ProtoObject, I subclassed from Object a ProxyObject with an iVar called encapsulatedObject, and then write<br><br>ProxyObject >>doesNotUnderstand: aMessage
<br> ^aMessage sendTo: self encapsulatedObject<br><br>Then for every message I need to intercept, I write:<br><br>ProxyObject >>at: index put: value <br> ^self doesNotUnderstand: (Message selector: #at:put: <br>
arguments: (Array with: index with: value)).<br><br>ProxyObject>>asString<br> ^self doesNotUnderstand: (Message selector: #asString).<br><br>ProxyObject>>name
<br> ^self doesNotUnderstand: (Message selector: #name).<br><br>....<br><br>ok... you get the idea.<br>But I was reading a paper called "Evaluating Message Passing Control Techniques in Smalltalk" from Stéphane Ducasse, and supposed my idea qualified as "minimal object". He wrote:
<br><br>"The right technique to create a minimal object is the following: <br>(1) creation of a subclass of Object,<br>(2) assignment of the superclass link to nil and<br>(3) definition of the minimal behavior by copying the needed methods from Object"
<br><br>But I've implemented it without (2) and doing some message replication mentioned above (currently I have no more than 15 of those kind of messages) it would, at first, bypass the problem described in the "Problems" section:
<br><br>"This leads to the problem of the interpretation by the minimal object of messages that were initially destined for the controlled object"<br><br>Hope I've understood the right way. However, something still smells bad to me... and that's why I'm writing to the list for some advice or suggestion. The only real problem I've experimented is when the replication of #ifNil: nilBlock takes place, this doesn't seem to work:
<br><br>ProxyObject>>ifNil: nilBlock<br> ^self doesNotUnderstand: (Message selector: #ifNil: argument: nilBlock).<br><br>(my guess here is there's some optimization thing walking around)<br><br>So, for those cool guys here, can you tell me if there is a possible drawback or unwanted behavior I'm not seeing? If true in which case would happen? Is this a valid way of implementing a Proxy or there's something I've missing? (I suspect a performance penalty, but I'm not sure about this)
</blockquote><div><br>Hi <span class="gmail_quote"><span class="gmail_sendername">Alejandro </span></span></div><br></div>I've got a pre-packaged, working version of a proxy. I've spent a long time trying to get it to work without crashing inspectors and debuggers, and it's still not perfect. Give it a try if you want:
<br><br><a href="http://www.squeaksource.com/DPON/MessageCapture-mvdg.9.mcz">http://www.squeaksource.com/DPON/MessageCapture-mvdg.9.mcz</a><br><br>Gulik.<br clear="all"><br>-- <br><a href="http://people.squeakfoundation.org/person/mikevdg">
http://people.squeakfoundation.org/person/mikevdg</a><br><a href="http://gulik.pbwiki.com/">http://gulik.pbwiki.com/</a>