Backbone View property not being set
===

I have a view with a property which i want to update its value when i make a fetch request.

        define(['underscore','backbone','models/taskCollection'],
        		function( _,Backbone,TaskCollection) {
        		var UserTasksView = Backbone.View.extend({
        			el:"#user-task-list",
        			cur_task: undefined,
        			initialize: function() {
        				this.collection = new TaskCollection;
        				this.model = this.collection._model;
        
        				_.bindAll(this,'render');
        				this.collection.bind('reset',this.render);
        			},
    view_task: function( event ) {
    				
    				var el = $(event.currentTarget);
    				var task_id = el.attr('data-taskid');
    				var row = el.parents('td').parents('tr.task-row');
    
    				row.addClass("active");
    
    				el.hide();
    				el.next('a').show();
    
    				var task = this.collection.fetch({
    					data: {id:task_id},
    					silent:true,
    					success:this._task_fetch_success
    				});
    
    				this._show_task_detail();
    
    				event.preventDefault();
    			},
    
    			_task_fetch_success: function(response,status,xhr) {
    				this.cur_task = JSON.stringify(status);
    				return status;
    			},
    
    			/**
    			* Displays the details of a task
    			**/
    			_show_task_detail: function() {
    				var main = $('.app-content');
    				var detail_view = $('.app-extra');
    				var task_detail_view = $("#task-detail-view");
    
    				//Reduce task list view width
    				main.animate({
    					"width":"50%"
    				},2000);
    				//Display app extra bar
    				detail_view.show();
    				//show task detail  view
    				detail_view.children('active-page').hide().removeClass('active-page').addClass('inactive-page');
    				task_detail_view.show().removeClass('inactive-page').addClass('active-page');
    				console.log(this.cur_task);
    				var template = ich.task_detail(this.cur_task)
    				$('div.task-details').html(template);
    			}
  

The ajax request trigger by the fetch is successful and success callback executes, but when i try to log "cur_task" property, it shows up as undefined;
What am i doing wrong