error TS2345: Argument of type 'X' is not assignable to parameter of type 'X[]'

Question

Currently, there is a strange behaviour when trying to create a new object in Typescript. There are two classes:

export class SkaterDrawn {

    private ID;
    private name;
    ...

constructor(input?:any) {
    this.ID = input.ID;
    ...
}


export class SkaterDrawnTeam extends SkaterDrawn {
    private skaters:SkaterDrawn[];

    constructor(skaters:SkaterDrawn[]) {
        super(skaters[0]);
        this.skaters = skaters;
    }
    ...
}

this.registeredSkaters contains an array of elements of type SkaterDrawn . Now I'm grouping this array into an array of chunks, like this:

this.registeredSkaters = this.registeredSkaters.groupBy('teamID');
this.registeredSkaters = Object.values(this.registeredSkaters);

This outputs:

[
    [SkaterDrawn,SkaterDrawn,SkaterDrawn],
    [SkaterDrawn,SkaterDrawn,SkaterDrawn],
    [SkaterDrawn,SkaterDrawn,SkaterDrawn]
]

Now I'm trying to create a new Object out of this:

let teams = this.registeredSkaters.map((item:SkaterDrawn[]) => 
    new SkaterDrawnTeam(item);
})

I expected to get an array of SkaterDrawnTeam , but the compilation fails with

ERROR in src/app/competition/components/drawing/drawing.component.ts(166,30): 
error TS2345: Argument of type 'SkaterDrawn' is not assignable to parameter of type 'SkaterDrawn[]'.
Type 'SkaterDrawn' is missing the following properties from type 'SkaterDrawn[]': length, pop, push, concat, and 35 more.

Line 166,30 is the line where I try to do new SkaterDrawnTeam(item) I don't know why this fails. What am I doing wrong and how can I fix it?

Thx so much for your help.

Answer 1

The problem was the SkaterDrawn[] is not same as (typeof SkaterDrawn)[]

let teams = this.registeredSkaters.map((item: (typeof SkaterDrawn)[]) => { 
               return new SkaterDrawnTeam(item);
             });

And then change your class as

export class SkaterDrawnTeam extends SkaterDrawn {
    private skaters:(typeof SkaterDrawn)[];

    constructor(skaters:(typeof SkaterDrawn)[]) {
        super(skaters);
        this.skaters = skaters;
    }
}

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