Add type safe get

Author: happycollision

addon/utils/type-safe-get.ts

@@ -0,0 +1,66 @@
+import { get } from '@ember/object';
+
+function arrayGet(obj: any, props: string[]) {
+  if (obj === undefined) return obj;
+  return get(obj as any, props.join('.')) as any | undefined;
+}
+
+function typeSafeGet<
+  T extends any, A extends keyof T, B extends keyof T[A], C extends keyof T[A][B], D extends keyof T[A][B][C], E extends keyof T[A][B][C][D], F extends keyof T[A][B][C][D][E], G extends keyof T[A][B][C][D][E][F], H extends keyof T[A][B][C][D][E][F][G]
+>(
+  object: T, prop1: A, prop2: B, prop3: C, prop4: D, prop5: E, prop6: F, prop7: G, prop8: H
+): T[A][B][C][D][E][F][G][H] | undefined
+
+function typeSafeGet<
+  T extends any, A extends keyof T, B extends keyof T[A], C extends keyof T[A][B], D extends keyof T[A][B][C], E extends keyof T[A][B][C][D], F extends keyof T[A][B][C][D][E], G extends keyof T[A][B][C][D][E][F]
+>(
+  object: T, prop1: A, prop2: B, prop3: C, prop4: D, prop5: E, prop6: F, prop7: G
+): T[A][B][C][D][E][F][G] | undefined
+
+function typeSafeGet<
+  T extends any, A extends keyof T, B extends keyof T[A], C extends keyof T[A][B], D extends keyof T[A][B][C], E extends keyof T[A][B][C][D], F extends keyof T[A][B][C][D][E]
+>(
+  object: T, prop1: A, prop2: B, prop3: C, prop4: D, prop5: E, prop6: F
+): T[A][B][C][D][E][F] | undefined
+
+function typeSafeGet<
+  T extends any, A extends keyof T, B extends keyof T[A], C extends keyof T[A][B], D extends keyof T[A][B][C], E extends keyof T[A][B][C][D]
+>(
+  object: T, prop1: A, prop2: B, prop3: C, prop4: D, prop5: E
+): T[A][B][C][D][E] | undefined
+
+function typeSafeGet<
+  T extends any, A extends keyof T, B extends keyof T[A], C extends keyof T[A][B], D extends keyof T[A][B][C]
+>(
+  object: T, prop1: A, prop2: B, prop3: C, prop4: D
+): T[A][B][C][D] | undefined
+
+function typeSafeGet<
+  T extends any, A extends keyof T, B extends keyof T[A], C extends keyof T[A][B]
+>(
+  object: T, prop1: A, prop2: B, prop3: C
+): T[A][B][C] | undefined
+
+function typeSafeGet<
+  T extends any, A extends keyof T, B extends keyof T[A]
+>(
+  object: T, prop1: A, prop2: B
+): T[A][B] | undefined
+
+function typeSafeGet<
+  T extends any, A extends keyof T
+>(
+  object: T, prop: A
+): T[A] | undefined
+
+function typeSafeGet<T extends any>(object: object, ...props: string[]): T | undefined {
+  return arrayGet(object, props) as T | undefined;
+}
+
+export function overrideGet<T extends any>(object: object, propPath: string): T | undefined
+export function overrideGet<T extends any>(object: object, ...props: string[]): T | undefined
+export function overrideGet<T extends any>(object: object, ...propPath: string[]): T | undefined {
+  return arrayGet(object, propPath) as T | undefined;
+}
+
+export default typeSafeGet;

tests/unit/utils/type-safe-get-test.ts

@@ -0,0 +1,36 @@
+import typeSafeGet, { overrideGet } from 'ember-typescript-utils/utils/type-safe-get';
+import { module, test } from 'qunit';
+
+module('Unit | Utility | type-safe-get', function(_hooks) {
+
+  test('it works', function(assert) {
+    const test = {a: {b: {c: {d: {e: {f: {g: {h: 'made it!'}}}}}}}};
+    
+    assert.deepEqual(typeSafeGet(test, 'a'), test.a);
+    assert.deepEqual(typeSafeGet(test, 'a', 'b'), test.a.b);
+    assert.deepEqual(typeSafeGet(test, 'a', 'b', 'c'), test.a.b.c);
+    assert.deepEqual(typeSafeGet(test, 'a', 'b', 'c', 'd'), test.a.b.c.d);
+    assert.deepEqual(typeSafeGet(test, 'a', 'b', 'c', 'd', 'e'), test.a.b.c.d.e);
+    assert.deepEqual(typeSafeGet(test, 'a', 'b', 'c', 'd', 'e', 'f'), test.a.b.c.d.e.f);
+    assert.deepEqual(typeSafeGet(test, 'a', 'b', 'c', 'd', 'e', 'f', 'g'), test.a.b.c.d.e.f.g);
+    assert.deepEqual(typeSafeGet(test, 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h'), test.a.b.c.d.e.f.g.h);
+  });
+
+  test('overrideGet also works', function(assert) {
+    const test = {a: {b: {c: {d: {e: {f: {g: {h: 'made it!'}}}}}}}};
+    
+    assert.deepEqual(overrideGet(test, 'a'), test.a);
+    assert.deepEqual(overrideGet(test, 'a', 'b'), test.a.b);
+    assert.deepEqual(overrideGet(test, 'a', 'b', 'c'), test.a.b.c);
+    assert.deepEqual(overrideGet(test, 'a', 'b', 'c', 'd'), test.a.b.c.d);
+    assert.deepEqual(overrideGet(test, 'a', 'b', 'c', 'd', 'e'), test.a.b.c.d.e);
+    assert.deepEqual(overrideGet(test, 'a', 'b', 'c', 'd', 'e', 'f'), test.a.b.c.d.e.f);
+    assert.deepEqual(overrideGet(test, 'a', 'b', 'c', 'd', 'e', 'f', 'g'), test.a.b.c.d.e.f.g);
+    assert.deepEqual(overrideGet(test, 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h'), test.a.b.c.d.e.f.g.h);
+  });
+
+  test('it returns undefined if the initial object is undefined', function(assert) {
+    let nothing!: {oops: 'this is just a type, not a value'};
+    assert.equal(typeSafeGet(nothing, 'oops'), undefined);
+  });
+});