Assigning array of objects into an interface based array

Question

I have this problem on assigning an array of objects to an interface based array

Currently I have this implementation on my interface item.ts

export interface IItem {
    id: number, text: string, members: any
}

and on the item.component.ts

export class ItemComponent {
    selectedItems: IItem[] = [];
    items: IExamItems;
    getSelected(): void {
        this.selectedItems = this.items.examItems.map(examItem=> examItem.item)
    }
}

it seems that i'm always getting this error

TS2322: Type 'IItem[][]' is not assignable to type 'IItem[]'.
Type 'IItem[]' is not assignable to type 'IItem'.
Property 'id' is missing in type 'IItem[]'.

Greg is right. If examItem.item is an IItem then please try a push each item and it should work. Do a console of this.items.examItems.map(examItem=> examItem.item) and you get the structure you are trying to assign. Seems like its a type mismatch — Gary
– Gary, Commented Jan 2, 2018 at 13:35
ah sorry forgot to include, but i've already declared it @Gary yes, thanks for pointing that out it is indeed a mismatch, and already got the solution as well Thank you :) — Hysteria
– Hysteria, Commented Jan 3, 2018 at 22:54

Greg Rozmarynowycz · Accepted Answer · 2018-01-02 10:59:29Z

2

Your assignment doesn't work because as the error states, the value has an incompatible type with the field. You can't assign IItem[][] to IItem[], as the former is an array of arrays of IItem and the latter is just an array of IItem. You either need to flatten the array or change the type of selectedItems field to IItem[][]. If you want to flatten the array, you can use Array.prototype.concat:

const itemArr = this.items.examItems.map(examItem=> examItem.item);
this.selectedItems = Array.prototype.concat.apply([], itemArr);

answered Jan 2, 2018 at 10:59

Greg Rozmarynowycz

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