Proper way of updating js-data relation objects

Question

I have a linked list of objects of the same type:

GET /cards.json

[{
  "id": 1,
  "lesserCardId": null,
  "greaterCardId": 2,
 }, {
  "id": 2,
  "lesserCardId": 1,
  "greaterCardId": 3
}, {
  "id": 3,
  "lesserCardId": 2,
  "greaterCardId": null
}]

Resource definition:

DS.defineResource({
  name: 'card',
  relations: {
    belongsTo: {
      card: [{
        localField: 'lesserCard',
        localKey: 'lesserCardId'
      }, {
        localField: 'greaterCard',
        localKey: 'greaterCardId'
      }]
    }
  }
});

js-data correctly reads json and creates object hierarchy. What I want next is to automatically update linked card properties like this:

var card1 = DS.get('card', 1);
var card4 = DS.inject('card', {'id': 4});
card1.greaterCard = card4;

// corresponding liked object properties should be updated automatically
expect(card4.lesserCard).toBe(card1);
expect(card2.lesserCard).toBeUndefined();

I have achieved this without js-data making custom setter like this:

Object.defineProperty(Card.prototype, 'greaterCard', {
  set: function (card) {
     // custom logic for updating linked list structure
     if (card === this.$greaterCard) {
       return;
     }
     this.$greaterCard.lesserCard = this.$lesserCard;
     this.$greaterCard = card;
     if (card) {
       card.lesserCard = this;
     }
     // updating depending properties
     this.$updateCardLevel();
     this.$updateCardLevelMax();
  },
  get: function () {
    return this.$greaterCard;
  }
});

But js-data introduces it's own property descriptors for relation objects. So this approach cannot be applied. I haven't found a way to hook into js-data relation property setters. I could make a separate service with method like cardService.setGreaterCard(card, greaterCard); which would update list structure, but this wouldn't be so convenient. Is there better way for updating linked objects on property change?

js-data version: 2.9.0

As a workaround solution added `card.setLesserCard(card);` and `card.setGreaterCard(card);`. Not pretty, but works. — Vlad-HC, May 31 '16 at 13:38

score 3 · Accepted Answer · answered Oct 21 '16 at 16:58

In JSData 2.x you would do this:

var Card = DS.defineResource({
  name: 'card',
  relations: {
    belongsTo: {
      card: [
        {
          localField: 'lesserCard',
          localKey: 'lesserCardId',
          link: false
        },
        {
          localField: 'greaterCard',
          localKey: 'greaterCardId',
          link: false
        }
      ]
    }
  }
});

Object.defineProperties(Card[Card.class].prototype, {
  lesserCard: {
    set: function (lesserCard) {
       this.lesserCardId = lesserCard.id;
       lesserCard.greaterCardId = this.id;
    },
    get: function () {
      return Card.get(this.lesserCardId);
    }
  },
  greaterCard: {
    set: function (greaterCard) {
       this.greaterCardId = greaterCard.id;
       greaterCard.lesserCardId = this.id;
    },
    get: function () {
      return Card.get(this.greaterCardId);
    }
  }
});

In JSData 3.x you would just do this:

store.defineMapper('card', {
  relations: {
    belongsTo: {
      card: [
        {
          localField: 'lesserCard',
          foreignKey: 'lesserCardId',
          set: function (Relation, card, lesserCard, originalSet) {
            lesserCard.greaterCardId = card.id;
            originalSet(lesserCard);
          }
        },
        {
          localField: 'greaterCard',
          foreignKey: 'greaterCardId',
          set: function (Relation, card, greaterCard, originalSet) {
            greaterCard.lesserCardId = card.id;
            originalSet(lesserCard);
          }
        }
      ]
    }
  }
});

Proper way of updating js-data relation objects

1 Answers1