Loads template files dynamically for a Marionette's Module.

ModuleHelper - simple

Marionette.ModuleHelper = (function(Marionette, _) {
    "use strict";

    var moduleHelper = { };

    moduleHelper.templatePath = 'templates/';
    moduleHelper.templateExt = ".html";
    moduleHelper.templatePrefix = "";

    
    moduleHelper.loadModuleTemplates = function (module, callback) {
        // walk the views in the provided module
        // gather the templates used by each view
        // then preload them all
        // when done, call the callback
        moduleHelper.templatePath = module.templatePath;
        moduleHelper.templatePrefix = module.prefix;

        var templatesToLoad = [];
        for (var viewName in module.views) {
            var view = module.views[viewName];
            templatesToLoad.push(view.prototype.template);
        }
        var loadingTemplates = moduleHelper.preloadTemplates(templatesToLoad, module);
        $.when(loadingTemplates).done(callback);
    };

    moduleHelper.preloadTemplates = function (templateIds, context) {
        // given a list of templateIds, queue each one for preloading
        // returns a jquery promise object which is resolved when all complete
        var loadAllTemplates = $.Deferred();
        var loadTemplatePromises = [];

        // queue each template for loading
        _.each(templateIds, function (templateId, index) {
            loadTemplatePromises[index] = moduleHelper
                .preloadTemplate(templateIds[index], moduleHelper);
        });
        
        // count down to 0 as templates are loaded, then resolve
        var templatesRemainingToLoad = loadTemplatePromises.length;
        _.each(loadTemplatePromises, function (aLoadPromise) {
            $.when(aLoadPromise).done(function () {
                templatesRemainingToLoad--;
                if (templatesRemainingToLoad == 0)
                    loadAllTemplates.resolveWith(context);
            });
        });
        
        return loadAllTemplates;
    };

    moduleHelper.preloadTemplate = function(templateId, context) {
        // preload a single template
        // returns a jquery promise
        var loader = $.Deferred();
        var msg;
        var err;

        if (!templateId || templateId.length == 0) {
            err = new Error('No templateId was specified.');
            err.name = "NoTemplateSpecified";
            throw err;
        }

        var url = moduleHelper.templatePath + templateId + moduleHelper.templateExt;

        $.get(url, function(serverTemplate) {
            if (!serverTemplate || serverTemplate.length == 0) {
                msg = "Could not find template: '" + templateId + "'";
                err = new Error(msg);
                err.name = "NoTemplateError";
                throw err;
            }

            moduleHelper.storeTemplate(templateId, serverTemplate);
            loader.resolveWith(context);

        });
        return loader;
    };


    moduleHelper.storeTemplate = function(templateId, template) {
        // compile template and store in cache
        template = Marionette.TemplateCache.prototype.compileTemplate(template);
        var cachedTemplate = new Marionette.TemplateCache(templateId);
        cachedTemplate.compiledTemplate = template;
        Marionette.TemplateCache.templateCaches[templateId] = cachedTemplate;
    };

    return moduleHelper;
})(Marionette,_);