customer.js

sc_require('models/record');

App.Customer = App.Record.extend({
	
  /**
    Walk like a duck
    
    @property {Boolean}
    @default YES
    @isReadOnly
  */
  isAppCustomer: YES,

  phoneNumbers: SC.Record.toMany('App.PhoneNumber', {inverse: 'customer', isMaster: YES})

}) ;

gistfile2.js

// Creation of a record

var customerId = 123;
var phoneNumber = App.store.createRecord(App.PhoneNumber, {
   customer: customerId
   /* ... */
});

phone_number.js

sc_require('models/record');

App.PhoneNumber = App.Record.extend({
  
  /**
    Walk like a duck
    
    @property {Boolean}
  */
  isAppPhoneNumber: YES,
  
  customer: SC.Record.toOne('App.Customer', {inverse: 'phoneNumbers', isMaster: NO}),
  
  /** @private
    Needed because one-to-many relationships aren't enforced yet
  */
  customerHasChanged: function() {
    this.toOneHasChanged('customer');
  }.observes('customer'),
  
  destroy: function() {
    this.destroyToOne('customer');
    sc_super();
  }

}) ;

record.js

/**
  This is the parent record that other records for this app will inherit from
*/
App.Record = SC.Record.extend({
  
  /**
    Walk like a duck
    
    @property {Boolean}
    @default YES
    @isReadOnly
  */
  isAppRecord: YES,
  
  /** @private
    Needed because one-to-many relationships aren't enforced yet
    
    @param {String} key The key of the toOne property
    @returns {void}
  */
  toOneHasChanged: function(key) {
    var rec = this.get(key),
        attribute = this[key],
        inverse = attribute.get('inverse'),
        type = attribute.get('typeClass');
    
    if (!SC.none(attribute) && !SC.none(inverse) && !SC.none(type) && !SC.none(rec)) {
      if (!rec.isAppRecord) {
        rec = App.store.find(type, rec);
      }
      
      if (rec && rec.get(inverse)) {
        rec.get(inverse).addInverseRecord(this);
      }
    }
  },
  
  /** @private
    Needed because one-to-many relationships aren't enforced yet
    
    @param {String} key The key of the toOne property
    @returns {void}
  */
  destroyToOne: function(key) {
    var rec = this.get(key),
        attribute = this[key],
        inverse = attribute.get('inverse'),
        type = attribute.get('typeClass');
    
    if (!SC.none(attribute) && !SC.none(inverse) && !SC.none(type) && !SC.none(rec)) {
      if (!rec.isAppRecord) {
        rec = App.store.find(type, rec);
      }
      
      if (rec && rec.get(inverse)) {
        rec.get(inverse).removeInverseRecord(this);
      }
    }
  }
});