Adding a new property to mongo after 'save' in Keystone - mongodb

Question

I recently found out how to change the value of an existing property and saving it to the mongo database when using Keystone JS (How to alter a value before storing it to the database in Keystone JS).
Now I need to add a new property and save it to the database during the same pre('save') phase.
The aims is to say, if the result (existing property) of a game is 'Won', then add a new property 'won' which is a boolean (true). If it matters, the reason I want this is because in a handlebars template I want to say {{#if won}}class="success"{{/if}}
Game.schema.pre('save', function(next) {
if (this.isModified('result')) {
if (this.result === 'Won') {
this.won = true;
}
}
next()
});
But nothing happens. I read that you can't add properties unless they've been set in the schema. So I tried adding Game.schema.set('won', false); above that, but still nothing.
Is there a simple way to do this?

Answer 1

You could look at Mongoose virtuals which are properties that you can get and set but that do not get persisted to the database:
Game.schema.virtual('won').get(function() {
return this.result === 'Won'
})
http://mongoosejs.com/docs/guide.html#virtuals
If you just want to use it in your template then you could also set a specific property on locals in your view.
Perhaps something like this:
...
exports = module.exports = function(req, res) {
var view = new keystone.View(req, res)
var locals = res.locals
locals.games = []
view.on('init', function(next) {
var query = {} // Add query here
Game.model.find(query).exec(function(err, games) {
// Handle error
games.forEach(function(game) {
game.won = game.result === 'Won'
})
locals.games = games
})
})
}
...