Uncaught TypeError: Can't add property 12, obj

Question

I can't seem to understand the error I am getting on my client application. I am subscribing to a graphql subscription and I am able to retrieve the updates but I am not being able to push the changes to the typescript array called "models:ModelClass[]" which is bound to the view.

Is there something I am missing or doing wrong?

models.component.ts

this.apollo.subscribe({
  query: gql`
    subscription {
      newModelCreated{
        _id
        name
        type
        train_status
        deploy_status
        data_path
        description
        created_at
        updated_at
      }
    }
  `
}).subscribe((data) => {
  console.log("CREATED: " + JSON.stringify(data.newModelCreated));
  console.log(data.newModelCreated);
  var temp:ModelClass = data.newModelCreated;
  this.models.push(temp);
});

model-class.ts

export interface ModelClass {
    _id: string;
    name: string;
    type: string;
    parameters: {
        alpha: number;
    };
    train_status: string;
    deploy_status: string;
    test_accuracy: string;
    created_at: number;
    updated_at: number;
}

Answer 1

I suppose this.models is an array returned by Apollo and you want to add new created object to your initial array ? If true, Apollo returns an immutable Object !

You have to clone the initial returned array. Something like in the subscribe function:

this.apollo
    .watchQuery({query: INITIAL_GQL_REQUEST})
    .subscribe((data) => {
        this.models = data.models.map((model) => {
            return {
                id: model.id, 
                name: model.name,
                another: model.another
            }
        })
    };
});

Then your subscription request will be able to add a created model to this plain javascript array.

PS: Not sure but I suppose Apollo returns immutable objects because they are stored in the store and depending on your fetch policy, it can miss store hits if your are able to mutate them.

Hope it helps