Working around loss of support for type constraint being self

Question

This is something I\'ve been doing in older versions of TypeScript and I use this method in C#, but it doesn\'t work in the latest 1.0 version of TypeScript.

Here\'s

Answer 1

I accepted Steve's answer because he suggested to use Base>, but I wanted to keep a copy of the code change that fixed the problem on Stack Overflow:

class Base> { // 1. Set as any
    children: Array;

    doAction() {
        this.children[0].promise();
    }

    promise(): T {
        return  this; // 2. cast to any
    }
}

class Child extends Base {
    public myString: string;
}

new Child().promise().myString;

This requires a cast to any, but it's not so bad since it's only in the base class. This change doesn't affect anything using the Child or Base classes, so overall it was a very ideal alternative.

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Update: In TS 1.7+ this can be done using a polymorphic this:

class Base {
    children: Array;

    doAction() {
        this.children[0].promise();
    }

    promise(): this {
        return this;
    }
}

class Child extends Base {
    public myString: string;
}

new Child().promise().myString;