Usematch data filtering

With Usematch v1.1.x (and later) comes the pre filtering support mentioned in the previous post. I’m pretty happy with it and it comes with a few unintended (but cool) side effects.

The basic setup for a data filter looks like this:

var data = {
	posts:[
		{ title: "First Post!", ...}
		{ title: "Second Post!", ...}
	],
	customFilter: function(data, named_params) {
		data = data.sort( ... )
		return data.slice(named_params.len || 10);
	}
}

And to use it from a template:

{{#posts @customFilter{len:5} }} ... {{/posts}}

So far, so good. I felt for ergo-cms, it was just as important to have a filter that could be applied to any kind of list (posts, authors, tags, etc, etc), and this is where the ‘automagic’ prefilter comes in, and has the format of section.prefilter defined in the data context:

var data = {
	posts:[
		{ title: "First Post!", ...}
		{ title: "Second Post!", ...}
	],
	'posts.prefilter: function(data, named_params) {
		data = data.sort( ... )
		return data.slice(named_params.len || 10);
	}
}

So, now the filter is always invoked, without the template designer doing anything:

{{#posts}} ... {{/posts}}

This of course, can have some grave consequences, and so by default ergo-cms’s filters won’t do anything, unless a ‘parameter’ is passed to the filter, which looks like:

{{#posts @{len:10} }} ... {{/posts}}

OR, to get the top 10 newest posts:

{{#posts @{len:10,sortBy:'date,desc'} }} ... {{/posts}}

OR, to get the top 10 tags by usage:

{{#tags @{len:10,sortBy:'length,desc'} }} ... {{/tags}}

I think this a very cool and very powerful feature that is simply missing from most of the cms systems out there. To make this even easier, by default ergo-cms will sort by posts in reverse order (by file date), and tags by their usage and categories by their name. Of course, as a user, these can be overridden easily by simply redefining the filter in your config.ergo.js file:

default_fields: {
	'tags.prefilter' : function(tags, params) { 
		// do custom stuff here
		return tags;
	}
}