HasOne not work, if key value is 0

[rvinokurov]

if have some relation:

  models.Task = Backbone.RelationalModel.extend({

        relations: [
        
            {
                type: Backbone.HasOne, 
                key: 'scaner',
                relatedModel: 'models.Tool'
            }
        ]
});

and a have three scanner models with ids 0,1 and 2
Code work perfect if id > 0, and don't work, if id === 0
I find code of function "findRelated" in Backbone-relational and change it:

 findRelated: function( options ) {
            var item = this.keyContents;
            console.log(item);
            var model = null;

            if ( item instanceof this.relatedModel ) {
                model = item;
            }
            else if ( item || item === 0 ) { //add null check
                model = this.relatedModel.findOrCreate( item, { create: this.options.createModels } );
            }

            return model;
        }

Can you append my fix or another solution for fix bug, when id === 0?

[grumpit]

So you want to alter the default behavior of JavaScript considering 0 === false/null/undefined??

[rvinokurov]

Sorry if my enlgish bad. No. From server, from database, I receive list of scanners. ID of first scanner is 0.

in current function code:

 findRelated: function( options ) {
            var item = this.keyContents;
            var model = null;

            if ( item instanceof this.relatedModel ) {
                model = item;
            }
            else if ( item) { 
                model = this.relatedModel.findOrCreate( item, { create: this.options.createModels } );
            }

            return model;
        }

id for scanner with ID === 0 (item) is false, and relation rule don't work, because "if(item)" return false, if value is integer 0. So i want to add type check: value is integer 0 or value undefined/null/empty string/NaN.

[PaulUithol]

You have a database that actually generates an id value that is 0? Funky, I've never seen that ;). Which database are you using?

That said, 0 should probably be valid for ids. Connected to #152 btw.

[PaulUithol]

0 is probably the only falsy value that should be allowed to act as an id? Unless your db also generates empty strings as ids? ;)

[rvinokurov]

DB in current project is MS SQL.I do not know why the id starts from 0 instead of 1.

Our DB developer said that the start value of autoincrement id in the database can be set to any value(ex 0, -100). It may be wrong conceptually, but the possibility exists

I think that is necessary to consider that "0" is not false value. But empty string, undefined, null, NaN false values, of course.

[PaulUithol]

Well, seems that it starts at 0 because your DB guy explicitly made it so; the default is 1 (see http://www.stemkoski.com/start-mysql-auto-increment-at-a-number-other-than-1/ and http://stackoverflow.com/questions/1142472/how-to-force-mysql-to-take-0-as-a-valid-auto-increment-value).

It should work now, but I still wouldn't recommend using it in practice.. plenty of software (like this...) that just checks for falsy-ness in the JS/Python/etc world.

[grumpit]

Agreed. Convention over configuration. This is an edge case IMHO

On Aug 2, 2012, at 8:39 AM, Paul Uitholreply@reply.github.com wrote:

Well, seems that it starts at 0 because your DB explicitly told it to; the default is 1 (see http://www.stemkoski.com/start-mysql-auto-increment-at-a-number-other-than-1/ and http://stackoverflow.com/questions/1142472/how-to-force-mysql-to-take-0-as-a-valid-auto-increment-value).

It should work now, but I still wouldn't recommend using it in practice.. plenty of software (like this...) that just checks for falsy-ness in the JS/Python/etc world.

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