Exploring the connection between Backbone.js and the localStorage plugin through the 'todo' example, focusing on the relationship between collections and models

Question

Exploring the connection between Backbone.js and the localStorage plugin through the 'todo' example, focusing on the relationship between collections and models

Check out this official sample app:

I'm puzzled by the connection between the collection and its property localStorage = new Store(..)

Shouldn't this belong in the model since you can't really do a collection.save() anyway?

Furthermore, I attempted to implement something similar, but encountered issues

var Person = Backbone.Model.extend({
        defaults: {
            name:'no-name',
            age:0
        }
});


var Persons = Backbone.Collection.extend({
        model: Person,
        localStorage: new Store('Persons'),
        initialize: function(){
            console.log('collection initialized');

        }
});

window.people = new Persons();

var p1 = new Person({name:'JC',age:24});
p1.save({text:'hello'}); //<--- Uncaught TypeError: Cannot read property 'localStorage' of undefined

Any guidance on resolving this dilemma would be appreciated.

javascript backbone.js

Answer 1

Answer №1

One key aspect is utilizing the .create() function within a collection to facilitate saving data to localStorage.

Check out the source code for a todo sample here:

createOnEnter: function(e) {
      var text = this.input.val();
      if (!text || e.keyCode != 13) return;
      Todos.create({text: text});
      this.input.val('');
    },

This feature then grants the model instance the ability to modify it by employing the .save({attr:value}) function.

If modelInstance.save() is called without specifying a localStorage property in the model's constructor function, an error message will pop up:

Uncaught TypeError: Cannot read property 'localStorage' of undefined

However, with the model now stored in localStorage via the collectionInstance.create() method, you can use modelInstance.save({attr:value}) to make changes.

To sum it up, while Models offer the save() function for persistence, Collections provide the create() function for the same purpose.

In order to utilize these functionalities, ensure that REST urls are configured correctly within the collection and model or initiate the localStorage plugin within the Constructor Function of either (depending on your setup).

Answer 2

One key aspect is utilizing the .create() function within a collection to facilitate saving data to localStorage.

Check out the source code for a todo sample here:

createOnEnter: function(e) {
      var text = this.input.val();
      if (!text || e.keyCode != 13) return;
      Todos.create({text: text});
      this.input.val('');
    },

This feature then grants the model instance the ability to modify it by employing the .save({attr:value}) function.

If modelInstance.save() is called without specifying a localStorage property in the model's constructor function, an error message will pop up:

Uncaught TypeError: Cannot read property 'localStorage' of undefined

However, with the model now stored in localStorage via the collectionInstance.create() method, you can use modelInstance.save({attr:value}) to make changes.

To sum it up, while Models offer the save() function for persistence, Collections provide the create() function for the same purpose.

In order to utilize these functionalities, ensure that REST urls are configured correctly within the collection and model or initiate the localStorage plugin within the Constructor Function of either (depending on your setup).

Answer 3

Answer №2

Dealing with a similar issue where I needed to save a collection loaded from LocalStorage, I implemented a save() method on my Collections that iterated through each model and triggered model.save().

MyCollection.save = ->
    @each (model) ->
        model.save()

However, there was a downside to this approach when using Backbone.LocalStorage. By simply removing a model from the collection at runtime, it wasn't deleted from local storage. Manually handling unmatched models for destruction somewhat undermined the purpose of Backbone.Collection.set(); which offers features like adding/merging/deleting.

To address this issue, one solution involved modifying Backbone so that Backbone.Collection.set() used destroy() instead of remove() for missing models. Another approach I took was having all models listen for their own 'remove' event and trigger their own 'destroy' method accordingly, making removals permanent.

class Model extends Backbone.Model
  initialize: ->
    @on 'remove', @destroy

These solutions meant that removing a model equated to permanently destroying it, which suited my needs. To customize this behavior, special conditions could potentially be created to manage model removal differently.

Answer 4

Dealing with a similar issue where I needed to save a collection loaded from LocalStorage, I implemented a save() method on my Collections that iterated through each model and triggered model.save().

MyCollection.save = ->
    @each (model) ->
        model.save()

However, there was a downside to this approach when using Backbone.LocalStorage. By simply removing a model from the collection at runtime, it wasn't deleted from local storage. Manually handling unmatched models for destruction somewhat undermined the purpose of Backbone.Collection.set(); which offers features like adding/merging/deleting.

To address this issue, one solution involved modifying Backbone so that Backbone.Collection.set() used destroy() instead of remove() for missing models. Another approach I took was having all models listen for their own 'remove' event and trigger their own 'destroy' method accordingly, making removals permanent.

class Model extends Backbone.Model
  initialize: ->
    @on 'remove', @destroy

These solutions meant that removing a model equated to permanently destroying it, which suited my needs. To customize this behavior, special conditions could potentially be created to manage model removal differently.

Exploring the connection between Backbone.js and the localStorage plugin through the 'todo' example, focusing on the relationship between collections and models

Answer №1

Answer №2

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