[jQuery] Object variables get lost when doing $.ajax

[jQuery] Object variables get lost when doing $.ajax


I've written a javascript class in which there is a function which
makes a ajax request.
But the callback function of this $.ajax don't know the objects
variables. Why is that.
It looks something like this:
function FileView(fbId, rootFolder, showFolders, type) {
    this.tmpVar = 'somuch';
    FileView.prototype.choseFolder = function(folderId, type,
showFolders)
    {
        alert(this.tmpVar); // displays somuch
        $.ajax({     type: "POST",
            url: "file.php",
            data: "actions",
            success: function(msg) {
                alert(this.tmpVar); // displays undefined
            }
        });
    }
}
What am I doing wrong. It could be something with my class - it's the
first time I'm doing oop in javascript.