Step 3

BreakOutMethodObject3.ts

// Step 3

 // !!! ->  extracted interface with the things the
 // object method uses from the original class
export interface PointRenderer {
    readonly colorId: number;
    drawPoint(x: number, y: number, color: Color): void;
}

// !!! -> the original class implements it
export class GDIBrush implements PointRenderer  {
    colorId: number;

    // A long method
    public draw(renderingRoots: Point[], colors: ColorMatrix, selection: Point[]): void {
        // !!! -> we wrote this line and used the IDE to generate the new class
        new Renderer(this, renderingRoots, colors, selection);

        // some more code in the method
        for (const point of renderingRoots) {
            // a lot more code in the loop
            this.drawPoint(point.x, point.y, colors.getColor(this.colorId));
        }

        // a lot more code in the method
    }

    drawPoint(x: number, y: number, color: Color): void {
        // some code to draw a point...
    }
}

export class Renderer {
    private readonly pointRenderer: PointRenderer;
    private readonly renderingRoots: Point[];
    private readonly colors: ColorMatrix;
    private readonly selection: Point[];

    // !!! -> the new class only see the new interface
    constructor(
        pointRenderer: PointRenderer,
        renderingRoots: Point[],
        colors: ColorMatrix,
        selection: Point[]
    ) {
        this.pointRenderer = pointRenderer;
        this.renderingRoots = renderingRoots;
        this.colors = colors;
        this.selection = selection;
    }
    
    public draw(): void {
        // some more code in the method
        for (const point of this.renderingRoots) {
            // a lot more code in the loop

            this.pointRenderer.drawPoint(point.x, point.y, this.colors.getColor(this.pointRenderer.colorId));
        }

        // a lot more code in the method
    }
}