#each with call to helper ignores first entry in array - coffeescript

Question

I'm trying to generate a menu with handlebars, based on this array (from coffeescript):
Template.moduleHeader.modules = -> [
{ "moduleName": "dashboard", "linkName": "Dashboard" }
{ "moduleName": "roomManager", "linkName": "Raumverwaltung" }
{ "moduleName": "userManager", "linkName": "Benutzerverwaltung" }
]
The iteration looks like this (from the html code):
{{#each modules}}
<li {{this.isActive this.moduleName}}>
<a class="{{this.moduleName}}" href="#">{{this.linkName}}</a>
</li>
{{/each}}
{{this.isActive}} is defined like this (coffeescript code again):
Template.moduleHeader.isActive = (currentModuleName) ->
if currentModuleName is Session.get 'module'
"class=active"
Based on Session.get 'module' the appropriate menu item is highlighted with the css class active.
On reload, the Session-variable module contains 'dashboard', which is the first entry in that array, however, it does not get the active-class. If I add an empty object as the first item to the modules-array, the 'dashboard'-item is properly highlighted.
The strange thing is, that the first item (dashboard) is rendered fine, but it does not have the active-class, which raises the impression, that the function this.isActive is not called for the first item.
Am I doing it wrong?

Answer 1

Really going out on a whim here but my traditional approach would be below. I don't know whether it will work but it was too big for a comment, yet again it's not a guaranteed fix. Let me know how it goes:
Replace the HTML with
{{#each modules}}
<li {{isActive}}>
<a class="{{moduleName}}" href="#">{{linkName}}</a>
</li>
{{/each}}
Replace the CS with
Template.moduleHeader.isActive = () ->
currentModule = this
currentModuleName = currentModule.moduleName
if currentModuleName is Session.get 'module'
"class=active"

Answer 2

If its rendering, the each block is working correctly. There must be an issue in the isActive helper. Most likely the if block isn't working as you think it should be. Put a console.log in there and see if it is entered, and put another inside the if (printf debugging). I find this is usually the easiest way to do quick debugging of handlebars helpers.
A useful helper in js for inspecting values inside of a context is as follows
Handlebars.registerHelper("debug", function(optionalValue) {
console.log("Current Context");
console.log("====================");
console.log(this);
if (optionalValue) {
console.log("Value");
console.log("====================");
console.log(optionalValue);
}
});
Then you can call this inside an each block and see all the values the current context/a specific value has.