Using a Typescript anonymous class in a type qualifier

Question

I'm attempting to create a generic table builder class. Within the table builder, I define an anonymous class which stores column definitions. I would like the table builder to store instances of these definitions in an array. Here is the simplified class definition I'm currently working with:

export class TableBuilder<T> {

  Column = class {
    constructor(public data: T) {}
  }

  private columns: Array<TableBuilder['Column']>

  column(data: T) {
    const col = new this.Column(data);
    this.columns.push(col);
  }
}

The line this.columns.push(col) throws a compile-time error: Argument of type '(anonymous class)' is not assignable to parameter of type 'typeof (anonymous class)'

Is there a way to define the columns member as an array of anonymous class instances? I can define it as type any[], but I would prefer a solution that preserves type enforcement of column entries.

Your code gives different errors in the typescript playground. Can you provide a complete example that shows the errors your getting there? — Alex Wayne
– Alex Wayne, Commented Jun 8, 2020 at 18:39

shadeglare · Accepted Answer · 2020-06-08 18:56:05Z

1

You have to define a custom constructor type which produces column objects with a specific interface. Something like that:

interface IColumn<T> {
    //define column interface here
}

interface IColumnConstructor<T> {
    new(data: T): IColumn<T>;
}

class TableBuilder<T> {
    private Column: IColumnConstructor<T> = class<T> {
        constructor(public data: T) { }
    }

    private columns: IColumn<T>[] = [];

    public column(data: T) {
        const instance = new this.Column(data);
        this.columns.push(instance);
    }
}

Your anonymous class<T> class must be compatible with the ColumnInterface<T> interface if this scenario.

answered Jun 8, 2020 at 18:56

shadeglare

7,5969 gold badges51 silver badges60 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

Using a Typescript anonymous class in a type qualifier

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related