Start implementation of model relations

src/util/collection/Collection.ts

@@ -16,8 +16,11 @@ type ComparisonFunction<T> = (item: CollectionItem<T>, otherItem: CollectionItem
 import { WhereOperator, applyWhere, whereMatch } from './where'
 
 const collect = <T>(items: CollectionItem<T>[]): Collection<T> => Collection.collect(items)
+const toString = (item: unknown): string => String(item)
+
 export {
     collect,
+    toString,
     Collection,
 
     // Types

src/util/support/types.ts

@@ -9,3 +9,12 @@ export type ParameterizedCallback<T> = ((arg: T) => any)
 
 /** A key-value form of a given type. */
 export type KeyValue<T> = {key: string, value: T}
+
+/** Simple helper method to verify that a key is a keyof some object. */
+export function isKeyof<T>(key: unknown, obj: T): key is keyof T {
+    if ( typeof key !== 'string' && typeof key !== 'symbol' ) {
+        return false
+    }
+
+    return key in obj
+}