Support client-side id generation

[bookshelf]

Support client-side id generation

[vjpr]

At the moment I'm using this hack:

  initialize: =>
    @on 'fetched', @onFetched

  onFetched: (model, resp, options) =>
    unless _.isEmpty resp
      @fetched = true

  isNew: =>
    not @fetched

I'm sure I will encounter lots of issues.

[studds]

I took a slightly different approach. Because the id is created client side, it will never be null. So I overrode the default isNew to check 'serverCreatedAt' instead and added timestamps to all my tables.

Originally I thought about hacking in some sort of 'upsert', but that seemed messy and inefficient (with postgres... other databases this might be a good option). Checking the serverCreatedAt column is a better match to the original design, but is still exposed to race conditions, though, so I'll need to add in some sort of intelligent retry - perhaps it's enough to revert to 'update' if 'insert' fails?

    // A model is new if it has never been saved to the server, and lacks an 'serverCreatedAt' date
    Bookshelf.Model.prototype.hasTimestamps = ['serverCreatedAt', 'serverUpdatedAt'];
    Bookshelf.Model.prototype.isNew = function () {
        console.log('serverCreatedAt', this.get('serverCreatedAt'));
        return !this.get('serverCreatedAt');
    };

[tgriesser]

Yeah, @studds that sounds like a good solution - for now, I think this feature is best implemented as a custom method that handles the fetch to check for existence and then handles the save. But this might be something I take a look at once more of the core functionality is squared away.

[jukkatupamaki]

I'm using generated UUIDs and because of existing conventions in Backbone and Bookshelf, the column name for the UUID is 'id'. I noticed that when setting the 'id' field manually in a model's initialize() method, the underlying updated only the 'updated_at' field.

I fixed this using the following override for isNew() and provided a boolean flagging whether the model is still new:

idSetButNew: false,

initialize: function(params) {
    if(this.isNew()) {
        this.set('id', uuid.v4());
        this.idSetButNew = true;
    }
    // more initialization stuff
},

isNew: function() {
    return !this.get('id') || this.idSetButNew;
}

I think it could be useful if Bookshelf provided some practices for using custom ID generators to avoid this kind of overrides.

[johanneslumpe]

I quickly want to chime in on this. I'm also using UUIDs, but it seems that it is not necessary to overwrite the isNew() function to achieve the desired behavior. By hooking into the saving event on the model we can generate an id after the insert/update method has been determined, like so:

initialize: function(params) {
    this.on('saving', this._generateId);
},

_generateId: function (model, attrs, options) {
    if (model.isNew()) {
      model.set(model.idAttribute, uuid.v4());
    }
}

This way there is no override involved and to me this does not feel messy or hackish. @tgriesser would you agree?

[jukkatupamaki]

@johanneslumpe: I think that's a good workaround. Way better than what I had.

[tgriesser]

Yeah @johanneslumpe - that looks like a good approach!

[sidazhang]

@johanneslumpe the issue with your approach seems to be that the point of client-side generated id is so that you know the id before the insert event. Now, we won't know it. Which renders it the same as a server SERIAL.