Calling non existing property in MongooseJS / NodeJS

Question

Calling non existing property in MongooseJS / NodeJS

If i have a schema in mongoose looking like this (an example):

Meta = new Schema
  type_id:Number,
  datahash: String,
  data: Schema.Types.Mixed

This is all good. I can query Meta.datahash and get the value back etc. But if i query Meta.OtherProp, then i will get an error, as the property does not exisit in the model.

In PHP you have magic methods (getters/setters) that can handle this.

Is there any way to do this in Mongoose (or NodeJS). Examples are very welcome :)

BR/Sune

EDIT: Lets say that data is an object like this:

{
  56:'somevalue',
  77:'Othervalue'
}

Now - is there any way that i can query directly into this like

Meta.data.56

and then get "somevalue" returned?

And is there again a way to avoid js error of i query

Meta.data.90

as the property does not exist?

node.js
mongoose

Answer 1

I haven't used Mongoose. But here are some patterns that you can use to set defaults in both synchronous and asynchronous cases.

var  DATA={ 56:'somevalue',  77:'Othervalue' };

// SYNC: from JS object
function getPropOrDefault(prop){
  var val = DATA[String(prop)];
  var ret = (val !== undefined ? DATA[String(prop)] : 'default');
  return ret;
};


// ASYNC: from mongoose
function getFromMongoose(key,fn){
//or something. idk how u query mongoose
  process.nextTick(function(){
    var val = DATA[String(key)];
    if(val === undefined) { fn(new Error('no_property')) }
    else{ fn(null, val) };
  });
};

function getMongoosePropOrDefault(prop, callback){
  getFromMongoose(prop, function(err, result){
    if(err){ 
      callback(err, 'default');
    } else {
      callback(null, result);
    };
  });
};


(function main(){
  console.log('DATA[77]: '+getPropOrDefault(77) );
  console.log('DATA[99]: '+getPropOrDefault(99) );
  getMongoosePropOrDefault(77, function(err, result){
    console.log('mongoose.data.77: '+result);
  });
  getMongoosePropOrDefault(99, function(err, result){
    console.log('mongoose.data.99: '+result);
  });
})();

Answer 2

Thanks for the replies.

It turns out that if i just set a default value for Meta.data, then i can query non existing properties in the data using the square brackets [] instead of dot notation:

Meta.data[88]

This solves my issue, which was actually related more to js than node or mongoose. Of course this does not work when query sub properties like:

Meta.data[88].something

unless 88 does exist. But again - thats just javascript...