Structural Typing

Info

Structural Typing is when the objects interface is determined by the methods and attributes it actually contains rather than explicit extends.

class PngImage {
	draw() { console.log('Drawing a PNG image'); }
	resize() { console.log('Resizing a PNG image'); }
}
 
class SvgImage {
	draw() { console.log('Drawing an SVG image'); }
}
 
interface Image {
	draw: () => void;
}
 
interface ResizableImage {
	resize: () => void;
}
 
// Interface segregation principle && Polymorphism && Structural Typing
// The client should not be forced to depend on methods it does not use
// The client should not be forced to implement methods it does not use
function drawImage(image: Image) { image.draw(); }