mirror of
https://github.com/vercel-labs/scriptc.git
synced 2026-10-23 06:10:02 +08:00
Chris Tate
022ac6eba9
Arrays whose elements are class-backed interface values are native arrays of the element capsules, so iteration, indexing and most array methods no longer go through the checked-dynamic array, and method calls receive a receiver they can dispatch. Methods without a native form for these elements run on the array's live dynamic view. A read of an interface property signature has the property's static type and reads the field of an implementing class directly. Accessors, object literals and JavaScript classes keep the checked property read.
71 lines
1.8 KiB
TypeScript
71 lines
1.8 KiB
TypeScript
// Arrays of interface values crossing into untyped code and JSON, and
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// stored in class fields and records: the untyped view is the same array,
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// writes through either side are visible to the other, and elements keep
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// their identity.
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interface Shape {
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area(): number;
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}
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class Circle implements Shape {
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r: number;
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constructor(r: number) {
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this.r = r;
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}
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area(): number {
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return 3 * this.r * this.r;
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}
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}
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class Square implements Shape {
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side: number;
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constructor(side: number) {
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this.side = side;
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}
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area(): number {
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return this.side * this.side;
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}
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}
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const shapes: Shape[] = [new Circle(1), new Square(2)];
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const view: unknown = shapes;
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console.log(Array.isArray(view), view === shapes);
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const untyped = view as unknown[];
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untyped.push(new Square(3));
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console.log(shapes.length, shapes[2]!.area());
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shapes.push(new Circle(2));
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console.log(untyped.length);
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function describe(value: unknown): string {
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return JSON.stringify(value);
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}
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console.log(describe(shapes));
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console.log(JSON.stringify({ shapes }));
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class Scene {
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items: Shape[] = [];
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add(shape: Shape): this {
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this.items.push(shape);
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return this;
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}
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total(): number {
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let sum = 0;
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for (const item of this.items) sum += item.area();
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return sum;
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}
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}
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const scene = new Scene().add(shapes[0]!).add(new Square(4));
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console.log(scene.items.length, scene.total(), scene.items[0] === shapes[0]);
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scene.items = shapes;
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console.log(scene.total(), scene.items === shapes);
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type Layer = { name: string; shapes: Shape[] };
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const layer: Layer = { name: "base", shapes };
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layer.shapes.push(new Square(1));
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console.log(shapes.length, layer.shapes === shapes);
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const parsed = JSON.parse("[1, 2]") as unknown[];
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console.log(parsed.length);
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shapes.length = 1;
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console.log(shapes.length, (view as unknown[]).length);
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