Using Event Aggregator to load a view with differe

I am new to backbone.js started with backbone a week ago. I had to make a demo. The main idea behind it is when the page is loaded, I need to show the courses,and by default the students list for the first course in the list. Here is the code to display the course list which is in course.js file

//Model

  var Course = Backbone.Model.extend({
    urlRoot: '/api/courses/',
    idAttribute: 'Id', 
    defaults:{
        Id: null,
        Name: ""        
    },
    validate: function (attr) {
        if (!attr.Name)
            return "Name is required";          
      }
});

var Courses = Backbone.Collection.extend({
    model: Course,
    url: '/api/courses'
});

//Views

var CourseList = Backbone.View.extend({
    tagName: 'ul',
    initialize: function () {
        this.collection.on('reset', this.renderAll, this);
        this.collection.on('add', this.render, this);
        this.collection.fetch();
        _.bindAll(this, 'renderAll', 'render');
        return this;
    },
    renderAll: function () {
        this.collection.each(this.render);
        $('#spnStdntCourseName').text('Students Enrolled in ' + this.collection.at(0).get("Name"));
    },
    render: function (model) {
        var item = new CourseItem({ model: model });
        this.$el.append(item.el);
    },

    events: {
        "click    #btnAddCourse": "createNewCourse",
        "keypress #txtNewCourse": "createOnEnter"
    },

    createOnEnter: function (e) {
        if (e.keyCode == 13) {
            this.createNewCourse();
        }
    },
    createNewCourse: function () {
        this.collection.create({ Name: this.$el.find('#txtNewCourse').val() });
        this.$el.find('#txtNewCourse').val('');
    }
});


var CourseItem = Backbone.View.extend({
    tagName: 'li',
    className: 'courseli',
    events: {
        'click .remove': 'deleteItem',
        'click .edit': 'showEdit',
        'click': 'courseClicked'
    },

    initialize: function () {
        this.template = _.template($('#course').html()),
        this.model.on('change', this.render, this);
        this.render();
    },
    render: function () {
        var html = this.template(this.model.toJSON());
        this.$el.html('').html(html);
    },

    courseClicked: function () {
        $('#spnStdntCourseName').text('Students Enrolled in ' + this.model.get("Name"));
        Vent.trigger('studentDetails',"how to load student list from here based on courseID...?");
    },

    showEdit: function (event) {
        event.preventDefault();
        Vent.trigger('edit', this.model);
    },
    deleteItem: function () {
        this.model.destroy();
        this.remove();
    }
});


var CourseEdit = Backbone.View.extend({
    el: '#courseEdit',
    events: {
        'click #save': 'save',
        'click #cancel': 'cancel'
    },
    initialize: function () {
        _.bindAll(this, 'render', 'save');
        Vent.on('edit', this.render);
        this.template = _.template($('#courseEditTemplate').html())
    },
    render: function (model) {
        var data, html;
        this.model = model;
        data = this.model.toJSON();
        html = this.template(data);
        this.$el.html(html)
        .show()
        .find('#name')
        .focus();
        this.model.on('error', this.showErrors, this);
    },
    save: function (event) {
        var self = this;
        this.model.save({
            'Name': this.$el.find('#name').val()
        }, {
            success: function () {
                alert('Saved!');
                if (!window.courses.any(function (course) {
                    return course.get('Id') === self.model.get('Id');
                })) {
                    window.courses.add(self.model);
                }
                self.$el.hide();
            }
        });
    },
    cancel: function () {
        this.$el.hide();
    },
    showErrors: function (model, error) {
        var errors = '';
        if (typeof error === 'object') {
            errors = JSON.parse(error.responseText).join('<br/>');
            alert(errors);
        }
        else {
            alert(error);
        }
    }
});

var Vent = _.extend({ }, Backbone.Events);
window.courses = new Courses();
$(function () {
  var edit = new CourseEdit(),
    list = new CourseList({
        collection: window.courses,
        el: '#coursesList'
    });
});

Please take a look at the 'courseClicked' function inside CourseItem View, it is supposed to load the students list when a course item is clicked.

Now I have my Student model and views in students.js as below

var Student = Backbone.Model.extend({
urlRoot: '/api/students/',
idAttribute: 'Id',
defaults: {
    Id: null
},
validate: function (attr) {
    if (!attr.Name)
        return "Name is required";
}
});

var Students = Backbone.Collection.extend({
model: Student,
url: '/api/students'
});

//Views

var StudentList = Backbone.View.extend({
tagName: 'ul',
initialize: function () {
    this.collection.on('reset', this.renderAll, this);
    this.collection.on('add', this.render, this);
    this.collection.fetch({ data: $.param({ courseId: 11 }) });
    _.bindAll(this, 'renderAll', 'render');
    return this;
  Vent.on('studentDetails', this.render);
},
renderAll: function () {
    this.collection.each(this.render);
},
render: function (model) {
    var item = new StudentItem({ model: model });
    this.$el.append(item.el);
},

events: {
    "click    #btnAddStudent": "createNewStudent",
    "keypress #txtNewStudent": "createOnEnter"
},

createOnEnter: function (e) {
    if (e.keyCode == 13) {
        this.createNewStudent();
    }
},
createNewStudent: function () {
    this.collection.create({ Name: this.$el.find('#txtNewStudent').val() });
    this.$el.find('#txtNewStudent').val('');
}

});

var StudentItem = Backbone.View.extend({
tagName: 'li',
className: 'studentli',
events: {
    'click .remove': 'deleteItem',
    'click': 'studentClicked'
},

initialize: function () {
    this.template = _.template($('#student').html()),
        this.model.on('change', this.render, this);
    this.render();
},
render: function () {
    var html = this.template(this.model.toJSON());
    this.$el.html('').html(html);
},

studentClicked: function () {
    var Id = this.model.get("Id");
},

deleteItem: function () {
    this.model.destroy();
    this.remove();
}

});

window.students = new Students();
$(function () {
   var studentDetails = new StudentList({
        collection: window.students,
        el: '#studentsList'
    });      
});

so inside document.ready I have studentDetails variable which loads the students list.Here is my problem as of now I have loaded the students list on page load by passing some hard code parameter inside fetch like below

 this.collection.fetch({ data: $.param({ courseId: 11 }) });

but what I need to show is, the student list for the first course in the courselist view when the page is loaded, and in later stages, the student list for each and every course item clicked.For that purpose if you can remember in the "courseClicked" function inside "CourseItem" view in course.js, I have used

 Vent.trigger('studentDetails',"how to load student list from here based on courseID...?");

studentDetails is the var that I have initialised in students.js(in the code above) like this

window.students = new Students();
$(function () {
var studentDetails = new StudentList({
    collection: window.students,
    el: '#studentsList'
});      
});

So when I trigger the studentDetails I defnitely be needing the student model inside my courseClicked function,which is not available in that context. I beleive you guys understood my problem from the above explanation. So how do I fix this...? Is the approach I followed wrong..? Any good alternative,need suggestions. Hope there is not too much noise in the question.

EDIT

var CourseList = Backbone.View.extend({
tagName: 'ul',
initialize: function () {
this.students = new Students();
var studentList = new StudentList({
  collection: this.students,
  el: '#studentsList'
});

this.collection.on('reset', this.renderAll, this);
this.collection.on('add', this.render, this);
this.collection.fetch();
_.bindAll(this, 'renderAll', 'render');
return this;
},

renderAll: function () {
    this.collection.each(this.render);
    $('#spnStdntCourseName').text('Students Enrolled in ' +    this.collection.at(0).get("Name"));
    this.students.fetch({ data: $.param({ courseId: this.collection.at(0).get("Id") }) });
},
render: function (model) {
this.$el.html("");
var item = new CourseItem({ model: model, students: this.students});
this.$el.append(item.el);   
}
})

I have made following changes

1.students in collection to this.students(inside initialize of "CourseList" view) in the below code

initialize: function () {
    this.students = new Students();
    var studentList = new StudentList({
        collection: this.students,
        el: '#studentsList'
    });

2.I have fetched the students inside renderAll function instead of render function because for every course item that is fetched the student is also fetched.I mean if there are 6 courses i get to see the students for course 0 in the collection 6 times

 renderAll: function () {
    this.collection.each(this.render);
    $('#spnStdntCourseName').text('Students Enrolled in ' +    this.collection.at(0).get("Name"));
    this.students.fetch({ data: $.param({ courseId: this.collection.at(0).get("Id") }) });

SubQuestion

In the "CourseList" we have initialize function as below

 initialize: function () {
    this.students = new Students();
    var studentList = new StudentList({
        collection: this.students,
        el: '#studentsList'
    });

The studentsList el is as below

<div id="studentsList" class="box">
<div class="box-head">
    <h2 class="left">
        <span id="spnStdntCourseName"></span>
    </h2>
</div>
<div>
 <input type="text" id="txtNewStudent" placeholder="Add New Student" />
    <button id = "btnAddStudent">+ Add</button>    
</div>       
</div>

whenever I do this.$el.html("") inside render function of StudentList view like below

var StudentList = Backbone.View.extend({
tagName: 'ul',

render: function (model) {
this.$el.html("");
    var item = new StudentItem({ model: model });
    this.$el.append(item.el);
},
......

I loose the button and textbox elements inside the studentsList el, and the ul is not shown when I view source code in my browser which I mentioned as tagName, but I do see li which is tagName for studentItem view.Can you say what I am doing wrong

Thanks for our patience

First, you want to let the CourseList view to keep track of a Students collection as well as a StudentList. The Students collection will be passed into each CourseItem view to fetch. After it renders all CourseItem, it will tell the Students collection to fetch the first course's students.

var CourseList = Backbone.View.extend({
  tagName: 'ul',
  initialize: function () {
    this.students = new Students();
    var studentList = new StudentList({
      collection: students,
      el: '#studentsList'
    });

    this.collection.on('reset', this.renderAll, this);
    this.collection.on('add', this.render, this);
    this.collection.fetch();
    _.bindAll(this, 'renderAll', 'render');
    return this;
  },

  render: function (model) {
    this.$el.html("");
    var item = new CourseItem({ model: model, students: this.students});
    this.$el.append(item.el);
    this.students.fetch({ data: $.param({ courseId: 0 }) }); // fetch the first
  },
  ...
})

The CourseItem will store the Students collection, and on being clicked, fetch the correct students using its model's id.

var CourseItem = Backbone.View.extend({
  ...
  initialize: function() {
    this.students = this.options.students;
  },
  ...
  courseClicked: function () {  
    $('#spnStdntCourseName').text('Students Enrolled in ' + this.model.get("Name"));

    var courseId = this.model.id;
    this.students.fetch({ data: $.param({ courseId: courseId }) });
  },
  ...
})

In StudentList view, you don't let it fetch by itself.

var StudentList = Backbone.View.extend({
  tagName: 'ul',
  initialize: function () {
      this.collection.on('reset', this.renderAll, this);
      this.collection.on('add', this.render, this);
      _.bindAll(this, 'renderAll', 'render');
      return this;
  },
  ...

  render: function() {
    this.$el.html(""); // Reset the view for new students
    var item = new StudentItem({ model: model });
    this.$el.append(item.el);
  }
})

Then in your main script:

window.courses = new Courses();

$(function () {
   var courseList = new CourseList({
        collection: window.course,
        el: '#courseList'
    });
});

DISCLAIMER: Untested codes.