Ioke dynamic reception
Ioke dynamic reception
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Ioke will, just as most other dynamic languages, have a way to achieve what Martin Fowler calls Dynamic Reception. For you who are not familiar with this term, it’s the same as the method_missing of Ruby, doesNotUnderstand of Smalltak, __getattr__ of Python, forward of Io, and so on.
It basically allow you to override what happens when the regular message sending fails for some reason. It’s more general in some languages than others. In particular, the Python, Smalltalk and Io versions are more powerful than Ruby’s, since they catch all message sends, not necessarily only those that would cause an invocation.
My problem isn’t really whether I should have it in Ioke. I will have it. It’s extremely useful and allows the implementation of lots of things that can be hard otherwise. The question is what to call it. I’m not totally comfortable with any of the names given to this functionality. I would like to have something that is higher level, basically.
To understand the reasoning behind my thinking, I’ll do a very quick description of the semantic model of Ioke. It’s actually quite simple.
Everything is a message passing. When you write the name of a local variable, you’re sending a message of that name to the current context. When you’re getting the value of something, you are passing a message, etc. Something like this: “foo = 13. foo println”, will first call the message “=”, with foo and 13 as parameters. The next line will send the “foo” message, and then the “println” message to the result of the first one. So in this case it’s obvious that foo is not a method. It’s just a simple value. But if I do this: “foo = method(13). foo println”, the result will be the same, except that when sending the “foo” message, it will actually activate the method inside it. The rule is that when sending a message to get a cell (all the properties/attributes/slots of Ioke are called cells), if that cell returns something that is activatable, it will be activated. There is also a way to get cells without activating them.
So there are two relevant names. Cells and message passing. My first thinking is that since the feature will only be called when a cell can’t be found, it could be called dynamicCell, to reflect that the result is dynamic instead of static. Another version is to just say unhandledMessage, because that is really what happens. A message is sent that no one handles. The third alternative is “forward”, which I like for the metaphor. When someone sends mail to a person not living at an address anymore, the people living there can do something dynamic with it, maybe forward it somewhere.
But I just don’t know which one of these are best… Any suggestions.
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