Finding an item in a subdocument array with Mongoose

Question

Finding an item in a subdocument array with Mongoose

I am trying to add an instance method to my MessageBoard model to tell me whether a given User is a member of that MessageBoard.

The MessageBoard schema contains

members: [{
    type: Schema.Types.ObjectId
    ref: 'User'
}]

But my instance method...

MessageBoardSchema.methods.isUserMember = function(user) {
    return (this.members.id(user));
};

...tells me that the method id does not exist on the object this.members.

I haven't been able to find a solution in other similar questions because I am using a reference rather than a nested Schema here.

node.js
mongodb
mongoose
mean-stack

Answer 1

id method works for embedded documents where you have real documents within you members array; what you have in this.members is an array of ObjecIds. I would recommend you to use underscore.js

If user is indeed a user_id:

MessageBoardSchema.methods.isUserMember = function(user) {
    var user_found = _.any(this.members, function(member){
         // Use toString() if you are dealing with ObjectIds since
         // new ObjectId("53fba4eb816bc772107552f0")==new ObjectId("53fba4eb816bc772107552f0")
         // outputs false
         return this.members.id.toString() == user.toString();
    });
    return user_found;
};

If user is indeed a user:

MessageBoardSchema.methods.isUserMember = function(user) {
    var user_found = _.any(this.members, function(member){
         // Use toString() if you are dealing with ObjectIds as explained
         return this.members.id.toString() == user.id.toString();
    });
    return user_found;
};