Reducible, nested tree paths to set dynamic nodes

[aultac]

A somewhat common use of a Monkey is to lookup an item from a list based on a "current" id, i.e.

var tree = Baobab({
  currentEventid: 12,
  events: {
    12: { info: 'about event 12' },
  },
  event: monkey({
    cursors: {
      currentEventid: [ 'currentEventid' ],
      events: [ 'events' ],
    },
    get: function(c) {
      return c.events[c.currentEventid],
    }
  }),
});
console.log(tree.get([ 'event' ]);
// prints: { info: 'about event 12' }

Works great for getting the current thing, not so great for setting some property of the current thing. I was thinking about something like this as a compact way to set information on the thing looked up by the monkey:

tree.set([ 'events', [ 'currentEventid' ], 'info' ], 'different info on 12!');
console.log(tree.get(['event']));
// prints: { info: 'different info on 12!' }

I've done it outside Baobab thus far like this:

var reducePath = function(tree, state_path) {
  return _.map(state_path, function(p) {
    if (!_.isArray(p)) return p;
    return tree.get(reducePath(p));
  });
};
tree.set(reducePath(tree, [ 'events', [ 'currentEventid' ], 'info']), 'different info!');

Is it worth considering adding support to Baobab (if it doesn't already exist?) for nesting arrays of paths inside tree paths?

[Yomguithereal]

Hello @aultac. This seems like a fine idea. Let me bring @jacomyal in this conversation.

[abalmos]

+1

[Yomguithereal]

I took a step back here and remembered that I already implemented something of the kind in v1 and it ended up to be a chaotic mess. Will need a lot of thinking before re-implementing something of the kind.

[abalmos]

@Yomguithereal Can I ask what some of those issues were?

[Yomguithereal]

Issues with dependencies. Because basically, such a cursor becomes a monkey in fact. That is to say you would expect such cursor to update whenever either its path or the reduced path is updated. And this is recursive.

[aultac]

Perhaps implementation could be simplified by treating the nested paths as monkeys themselves? That's what I have to do manually now in a tree for such lookups. The advantage here is that full knowledge of the path should allow for a '2-way' monkey that supports set as well as get

[gersongoulart]

Would it be the case to create a set method in the monkey? As I was reading, this idea came to my mind:

var tree = Baobab({
  currentEventid: 12,
  events: {
    12: { info: 'about event 12' },
  },
  event: monkey({
    cursors: {
      currentEventid: [ 'currentEventid' ],
      events: [ 'events' ],
    },
    get: function(c) {
      return c.events[c.currentEventid],
    },
    set: function(path, data) {
       // In here you can do whatever updates to the tree you may possibly wish for, eg.:
        var currentEventid = tree.get('currentEventid');
        tree.set(['events', currentEventid, path], data)
    }
  }),
});

tree.select([ 'event' ]).set('info', 'different info!');

Just food for thought...

[Yomguithereal]

You don't need set in monkeys to perform what you want to do. Just listen to a cursor or a watcher and perform writes on the tree on their update events.