reverseRelation Collection is always instanceof Backbone.Collection

[mauron85]

Description: reverseRelation Collection is always instanceof Backbone.Collection

Expected: reverseRelation Collection is instanceof Routes
Actual: reverseRelation Collection is instanceof Backbone.Collection only

How to reproduce:

jsFiddle example: http://jsfiddle.net/mauron85/8uhvyq9L/

var User = Backbone.RelationalModel.extend({
        defaults: {
            routes: []
        }
});

var Route = Backbone.RelationalModel.extend({
    relations:[{
            type: Backbone.HasOne,
            key: 'user',
            relatedModel: User,
            includeInJSON: 'id', //serialize only id not a full object
            reverseRelation: {
                key: 'routes',
                includeInJSON: 'id'
            }        
    }]
});

var Users = Backbone.Collection.extend({
    model: User,
  url: '/users'
});

var Routes = Backbone.Collection.extend({
    model: Route,
    url: '/routes',
    someMethod: function () {
        console.log('you just called some method');
    }
});

var userJSON = [{
    id: 'john'
},{
    id: 'pete'
}];

var routesJSON = [{
    id: 'first',
    user: 'pete'
},{
    id: 'second',
    user: 'john'
}];

var users = new Users(userJSON);
var routes = new Routes(routesJSON);

var johnRoutes = users.at(0).get('routes')
console.log(johnRoutes.at(0).get('id') === 'second'); // TRUE
console.log(johnRoutes instanceof Backbone.Collection); // TRUE,
console.log(johnRoutes instanceof Routes); // FALSE, we cannot call Routes methods!!!

johnRoutes.someMethod(); // Uncaught TypeError: johnRoutes.someMethod is not a function

Modified version with model collection as constructor option throws:
Uncaught TypeError: collection.on is not a function
jsFiddle: http://jsfiddle.net/mauron85/8uhvyq9L/4/

[mauron85]

The problem seems to be hardcoded collectionType: Backbone.Collection

Backbone.HasMany = Backbone.Relation.extend({
    collectionType: null,

    options: {
        reverseRelation: { type: 'HasOne' },
        collectionType: Backbone.Collection, // HARDCODED
        collectionKey: true,
        collectionOptions: {}
    },
...

[mauron85]

Adding test scenario into Backbone-relational test suite:

https://rawgit.com/mauron85/Backbone-relational/issue-536/test/index.html

[ambischof]

do this:

    relations:[{
            type: Backbone.HasOne,
            key: 'user',
            relatedModel: User,
            includeInJSON: 'id', //serialize only id not a full object
            reverseRelation: {
                key: 'routes',
                includeInJSON: 'id',
                **type: Backbone.HasOne** <-----
            }        
    }]

If the relation should be bidirectional, specify the details for the reverse relation here. It's only mandatory to supply a key; relatedModel is automatically set. The default type for a reverseRelation is HasMany for a HasOne relation (which can be overridden to HasOne in order to create a one-to-one relation), and HasOne for a HasMany relation.

[mauron85]

Thank you. But my reverseRelation is HasMany. Or in words User can have many Routes.

[ambischof]

Ah sorry, seemed I misunderstood the problem.

Why haven't you used the option collectionType? (http://backbonerelational.org/#relations-collectionType)

[mauron85]

Thank you. That solved my problem.

Actually I thought I have tried to use collectionType some time before.
Apparently I did some mistakes, because this example works:

http://jsfiddle.net/mauron85/8uhvyq9L/12/

I'll leave this issue open. Because i think, following notice should be mentioned in the docs somewhere:

_"Reverse relation collection DOES NOT inherit it's collection type from relation it is reverse to. If you use reverseRelation, please make sure, you also specify collectionType. If you don't provide it, reverse collection type will be Backbone.Collection"_

And also my examples, might be helpful:
http://jsfiddle.net/mauron85/8uhvyq9L/
http://jsfiddle.net/mauron85/8uhvyq9L/12/