✨ add cacheGetter decorator

Author: saby1101

src/decorators/cache-getter.spec.ts

@@ -0,0 +1,21 @@
+import { cacheGetter } from "./cache-getter";
+
+test("cacheGetter should ensure getter is called only first time", () => {
+  let callCount = 0;
+  class Sample {
+    private readonly data: number[] = [1, 2, 3, 4, 5];
+
+    @cacheGetter
+    get sum(): number {
+      callCount++;
+      return this.data.reduce((acc, curr) => acc + curr, 0);
+    }
+  }
+
+  let s = new Sample();
+  expect(callCount).toBe(0);
+  expect(s.sum).toBe(15);
+  expect(callCount).toBe(1);
+  expect(s.sum).toBe(15);
+  expect(callCount).toBe(1);
+});

src/decorators/cache-getter.ts

@@ -0,0 +1,23 @@
+/**
+ * Cache output of getter
+ * @param value
+ * @param context
+ * @returns
+ */
+export function cacheGetter<This, Return>(
+  value: (this: This) => Return,
+  context: ClassGetterDecoratorContext,
+): (this: This) => Return {
+  if (context.kind !== "getter") {
+    return value;
+  }
+
+  return function (this: This) {
+    const returnValue = value.call(this);
+    Object.defineProperty(this, context.name, {
+      value: returnValue,
+      writable: false,
+    });
+    return returnValue;
+  };
+}

src/decorators/index.ts

@@ -0,0 +1 @@
+export { cacheGetter } from "./cache-getter";

src/index.ts

@@ -2,3 +2,4 @@ export * as Lang from "./lang";
 export * as Graph from "./graph";
 export * as BinPack from "./binpack";
 export * as Geo from "./geo";
+export * as Decorators from "./decorators";