CODEWITHSUNDEEP
typescripttypescript2.0
POV
POV

Reputation: 12015

Could Map has key as custom type?

I have custom interface type:

export interface IDictionary {
    id: number;
    dbVersion: number;
    code: string;
    tableName: string;
    name: Name;
    shortName: ShortName;
    active: boolean;
    restricted: boolean;
    hierarchy: boolean;
    metadata: string;
    rights: any[];
}

And I tried to build Map():

 dataMap = new Map<IDictionary, IDictionary[]>([
    [{ name: { ru: "Root1"}} as IDictionary, [{ name: { ru: "Papa"}} as IDictionary]]
  ]);

Is it possible to use key as IDictionary type?

Then I try to get values by key:

this.dataMap.get(node);

Where node is object:

{ name: { ru: "Root1"}}

I should get: [{ name: { ru: "Papa"}}]

Upvotes: 0

Views: 106

Answers (1)

Medet Tleukabiluly
Medet Tleukabiluly

Reputation: 11930

In JavaScript (and as an extension, TypeScript), no two objects are equal except if they refer to the same object. If you create a new object, it would not consider it to be equal to any existing one.

Because Maps consider such equality when looking up elements, if you store a value with an object as a key, you can only get the value out again if you pass in the exact same object reference as a key again:

interface Name {
  ru: string
}
interface ShortName extends Name {}
interface IDictionary {
  id?: number;
  dbVersion?: number;
  code?: string;
  tableName?: string;
  name: Name;
  shortName?: ShortName;
  active?: boolean;
  restricted?: boolean;
  hierarchy?: boolean;
  metadata?: string;
  rights?: any[];
}

const node = { name: { ru: 'Root1' } }

const dataMap = new Map<IDictionary, IDictionary[]>([[
  node, [{ name: { ru: 'Papa' } }]
]])

console.log(dataMap.get({ name: { ru: 'Root1' } })) // undefined
console.log(dataMap.get(node))                      // [ { name: { ru: 'Papa' } } ]

credits

Upvotes: 4

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