Populating Class[] with JSON in TypeScript

Question

As part of my model I have this class in TypeScript:

module App.Model {

    export class Unit {
            id: number;
            participantId: number;
            name: string;
            isProp: boolean;
        }
}

In the controller, I need a a hash with the id as key:

module App.Controllers {
    export class MyController {

        public units: App.Model.Unit[];

        populateDemoData() {
            this.units = {
                "1": { "id": 1, "participantId": 1, "name": "Testname", "isProp": true },
                "2": { "id": 2, "participantId": 1, "name": "Another name", "isProp": false }
            };
        }
    }
}

However, compiling the controller, I get the following error message:

Error 2 Cannot convert '{  }; [n: number]: App.Model.Unit; }' to ' }; [n: number]: App.Model.Unit; }' is missing property 'concat' from type 'App.Model.Unit[]'.

What am I doing wrong? And why is TypeScript asking for a concat property?

thoughtrepo · Accepted Answer · 2014-02-12 16:39:49Z

3

You defined units as an Array object, but assigned it a literal object. Just to clarify, a hash (a literal object) is not an array.

If all the IDs are an integer you can still use the array but it would be like this instead:

populateDemoData() {
    this.units = [];
    this.units[1] = { "id": 1, "participantId": 1, "name": "Testname", "isProp": true };
    this.units[2] = { "id": 2, "participantId": 1, "name": "Another name", "isProp": false };
}

Edit:

Ok, you have to define a hash table to do that, but you also need to make App.Model.Unit an interface that matches your JSON objects.

module App.Model {

    export interface Unit {
        id: number;
        participantId: number;
        name: string;
        isProp: boolean;
    }

    export interface UnitHashTable {
        [id: string]: Unit;
    }
}

module App.Controllers {

    export class MyController {

        public units: App.Model.UnitHashTable;

        populateDemoData() {
            this.units = {
                "1": { "id": 1, "participantId": 1, "name": "Testname", "isProp": true },
                "2": { "id": 2, "participantId": 1, "name": "Another name", "isProp": false }
            };
        }
    }
}

edited Feb 12, 2014 at 16:39

answered Feb 12, 2014 at 15:42

thoughtrepo

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2 Comments

Peter Albert Over a year ago

thanks for your answer. How would I define the units as a hash? I meant hash! I was playing around with the definition, originally it was units: App.Model.Unit[] producing the same error. I update the question, sorry!

Peter Albert Over a year ago

Looks great, thanks. I'll check later tonight when back online!

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