The reason why Type zzz cannot be assigned to type (zzz & NgIterable<xxx>) | undefined | null

Why am I receiving the message in Angular 9 that says: Type Items is not assignable to type (Items & NgIterable) | undefined | null?

Despite the fact that the model is correct and there are no errors in the data, I still encounter this TypeScript warning.

Here is the structure of myData model:

interface Item {
  url: string;
  label: string;
}

export interface Items {
  [key:number]: Item ;
}

My HTML code snippet:

<ng-container *ngFor="let card of myData"><!-- the warning occurs here -->
some content
</ng-container>

UPDATED: I realized that I forgot to provide an example data to clarify the situation. Here is an array as an example:

[
    {
      url: 'todo',
      label: 'Rekeningnummer'
    },
    {
      url: 'todo',
      label: 'Postadres'
    }] 

Answer №1

After some troubleshooting, I was able to solve the issue by changing the variable declaration from Items to Item[].

myData: Item[] = [...]

It came to my attention that indexes in the format [key: string]: T are always optional, making it impossible to use ? to indicate an empty array.

export interface Items {
  [key:number]?: Item ;
}

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