I have a user model schema in mongoose which contains a list of friends and groups and stats
info like so...
var user = new Schema({
email: { type: String, required: true, unique: true },
password: { type: String, required: true, select: false },
roles: [{ type: String, required: true }],
friends: [{ type: Schema.Types.ObjectId, ref: 'User' }],
groups: [{ type: Schema.Types.ObjectId, ref: 'Group' }],
stats : {
nbrFriends: { type: Number, required: false },
nbrGroups: { type: Number, required: false }
}
}, {
timestamps: true
});
I need to update the users stats
whenever a change is made to the friends
or groups
fields to contain the new number of friends
or groups
etc. For example, when the following function is called on a user:
var addGroup = function(user, group, cb) {
user.groups.push(group);
User.findOneAndUpdate({ _id: user._id }, { $set: { groups: user.groups }}, { new: true }, function(err, savedResult) {
if(err) {
return cb(err);
}
console.log('updated user: ' + JSON.stringify(savedResult));
return cb(null, savedResult);
});
};
How could I make sure the stats
is automatically updated to contain the new number of groups
the user has? It seems like a middleware function would be the best approach here. I tried the following but this never seems to get called...
user.pre('save', function(next) {
var newStats = {
nbrGroups: this.groups.length,
nbrPatients: this.friends.length
};
this.stats = newStats;
this.save(function(err, result) {
if(err) {
console.log('error saving: ' + err);
} else {
console.log('saved');
}
next();
});
});
You need to use the middleware a.k.a. hooks:
Middleware (also called pre and post hooks) are functions which are passed control during execution of asynchronous functions.
See the docs: