Saturday, September 10, 2005

XML Generation In Smalltalk

Tim Jones showed a simple way to generate XML in Smalltalk. And then Michael Lucas-Smith showed an even simpler way which is very close to what Seaside does for HTML generation (using #doesNotUnderstand:). In fact, I wrote one for Squeak a long time ago for myself that does exactly what Michael and Tim did (my DNU code calls the Tim-like code and compiles it on the fly so to make debugging easy and future hits quick). Anyway, I found that I needed something different for attributes so I created the ability to churn out XML from arrays. Here's some code from one on my tests:
xml := BtbXmlRenderer on: writeStream.
xml render: #(first arg1: 'value1' arg2: 'value2'
(second (third '"fun"'))
(fifth #sixth: 56)).

And this generates the following XML:
<?xml version="1.0"?>
<first arg1="value1" arg2="value2">
<fifth sixth="56"/>

I made all objects implement #renderXMLOn: so that I can use Arrays, Blocks, or anything else to make it easier to output XML in the future. It also means I can use all three approaches to generate one XML document. I think this is a perfect example of polymorphism and the power of dynamic languages at its finest. So, we have three ways of generating XML and I found that each has its advantages at different times. My point to this post was to show yet another way to generate XML using Smalltalk. Keep the Smalltalk flowing!

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