Ember.js 如何为模型添加/删除hasMany关系？

假设我有两个模型：User和Book

用户

var User = DS.Model.extend({
    name: DS.attr('string'),
    books: DS.hasMany('book')
});

书籍

var Book = DS.Model.extend({
    title: DS.attr('string'),
    users: DS.hasMany('user')
})

所以我希望能够为某个用户“结账”并归还书籍。鉴于以下BookController，在不实际删除书籍的情况下删除和添加关系的最佳做法是什么

var BookController = Ember.ObjectController.extend({
    needs: ['userProfile'],
    actions: {
        checkOutBook: function(){
            var currentBook = this.get('model');
            var userBooks = this.get('controllers.userProfile.model.books');
            //add relationship to user
        },
        returnBook: function() {
            var currentBook = this.get('model');
            var userBooks = this.get('controllers.userProfile.model.books');
            //remove relationship to user
        }
    }
})

使用

Ember 1.5.1

和

Ember数据1.0.0-beta.8.2a68c63a

//add
userBooks.pushObject(currentBook);

//remove
userBooks.removeObject(currentBook)