tabs.html

<style type="text/css">
body {font-family: verdana}
tabs {
	margin-top: 20px;
}
button {clear: both;}
tabs ul {
    padding: 0px; margin: 0px;
}
tabs li {
    float: left;
    padding: 10px;
    background-color: #F6F6F6;
    list-style: none;
    margin-left: 10px;
}
tabs li {
    color: #1C94C4;
    font-weight: bold;
    text-decoration: none;
}
tabs li.active {
    color: #F6A828;
    cursor: default;
}
panel {
   
    clear: both;
    display: block;
}
/* clearfix from jQueryUI */
tabs ul:after  { content: "."; display: block; height: 1px; clear: both; visibility: hidden; }
tabs ul { display: inline-block; }
</style>
<div id="demo-html">
<div id='out'></div>
<script id="app" type="text/mustache">
  <p><button can-click="addVegies">Add Vegetables</button></p>
  <tabs>
    {{#each foodTypes}}
      <panel title='{{title}}'>{{content}}</panel>
    {{/each}}
  </tabs>
</script>
</div>
<script src="../../lib/steal/steal.js"></script>
<script id="demo-source">
steal("can/component",function(){
	
can.Component.extend({
	tag: "tabs",
	template: 	
		"<ul>"+
			// Create an LI for each item in the panel's scope object
    		"{{#panels}}"+
    			"<li {{#isActive}}class='active'{{/isActive}} "+
    			    "can-click='makeActive'>"+
    			  "{{title}}"+
    			"</li>"+
    		"{{/panels}}"+
    	"</ul>"+
    	"<content></content>",
	scope: {
		// Contains a list of all panel scopes within the
		// tabs element.
		panels: [],
		// When a `<panel>` element is inserted into the document,
		// it calls this method to add the panel's scope to the
		// panels array.
		addPanel: function(panel){
			// If this is the first panel, activate it.
			if( this.attr("panels").length === 0 ) {
				this.makeActive(panel)
			} 
			this.attr("panels").push(panel);
		},
		// When a `<panel>` element is removed from the document,
		// it calls this method to remove the panel's scope from
		// the panels array.
		removePanel: function(panel){
			var panels = this.attr("panels");
			can.batch.start();
			panels.splice(panels.indexOf(panel),1);
			// if the panel was active, make the first item active
			if(panel === this.attr("active")){
				if(panels.length){
					this.makeActive(panels[0]);
				} else {
					this.removeAttr("active")
				}
			}
			can.batch.stop()
		},
		makeActive: function(panel){
			this.attr("active",panel);
			this.attr("panels").each(function(panel){
				panel.attr("active", false)
			})
			panel.attr("active",true);
			
		},
		// this is scope, not mustache
		// consider removing scope as arg
		isActive: function( panel ) {
			return this.attr('active') == panel
		}
	}
});

can.Component.extend({
	template: "{{#if active}}<content></content>{{/if}}",
	tag:"panel",
	scope: {
		active: false,
		title: "@"
	},
	events: {
		inserted: function(){
			this.element.parent().scope().addPanel( this.scope );
		},
		removed: function(){
			this.element.parent().scope().removePanel( this.scope );
		}
	}
})

var foodTypes= new can.List([
	{title: "Fruits", content: "oranges, apples"},
	{title: "Breads", content: "pasta, cereal"},
	{title: "Sweets", content: "ice cream, candy"}
])
window.foodTypes = foodTypes;

$("#out").html( can.view("app",{
	foodTypes: foodTypes,
	addVegies: function(){
		foodTypes.push({
			title: "Vegetables",
			content: "Carrots, peas, kale"
		})
	}
}))


})
</script>