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Question

I'd like to extend this example that parse.com gives in its tutorials to work with backbone collections and a second level of data (comments). Right now the exmaple is retrieving a list of posts for a user, with the following data structure:

USER
--------------------------------------
| User_ID |  Username | ......
--------------------------------------
| 1       |  John     | ........
| 2       |  Jane     | ........


POST 
--------------------------------------
| POST_ID  |  User_ID | Title    | .....
--------------------------------------
| 20       |  1       | abcdefg  | .....
| 21       |  1       | svsvdsv  | .....

I'd to extend this call to also return corresponding comments to each post. Meaning there would be one api call to parse that returns all the posts and all the comments to those posts (properly nested) for the logged in user. Below is an example of a comment data structure:

COMMENT
-----------------------------------------------------------------------
| COMMENT_ID  |  POST_ID  |  Comment_Text        | Title    | .....
-----------------------------------------------------------------------
| 30          |  21       |  awesome post woohoo | abcdefg  | .....
| 31          |  21       |  terrible post....   | svsvdsv  | .....

Any help would be greatly appreciated!

Answer 1

Backbone.js not support nested models so you can use Backbone-relational.js for nested models,

Backbone-relational.js provides one-to-one, one-to-many and many-to-one relations between models for Backbone Backbone Relation

classes

User = Backbone.Relational.Model({
    defaults : {
        id : '',
        name : '',
        posts : [], //collection
    },
    relation : [{
        type : 'HasMany',
        key : 'posts',
        relatedModel : 'com.dw.attendance.model.Post',
        reverseRelation : {
            key : 'user'
        }
    }]
});

Post = Backbone.Relational.Model({
    defaults : {
        id : '',
        user : '', //model
        comments : '', //collection
        title : '',
    },
    relation : [{
        type : 'HasOne',
        key : 'user',
        relatedModel : 'com.dw.attendance.model.User',
        reverseRelation : {
            key : 'posts'
        }
    },{
        type : 'HasMany',
        key : 'comments',
        relatedModel : 'com.dw.attendance.model.Comment',
        reverseRelation : {
            key : 'post'
        }
    }]
});


Comment = Backbone.Relational.Model({
    defaults : {
        id : '',
        post : '',//model
        text : '',
        title : ''
    },
    relation : [{
        type : 'HasOne',
        key : 'post',
        relatedModel : 'com.dw.attendance.model.Post',
        reverseRelation : {
            key : 'comments'
        }
    }]
});

your data like this, for user : {id : 1, name : 'john', posts : [1,2,3]};

then you can get, comments of any user post by,

user.get('posts').get('post_ID').get('comments');