makeLinkClass

src/tests.ts

@@ -27,6 +27,10 @@ abstract class Identified<ID> {
     equals(el: Identified<ID>) {
         return this.id === el.id
     }
+
+    // initializer() {
+    //     console.log("Identified initializer")
+    // }
 }
 
 class ImplementsIdentifiable<ID> extends Identified<ID> {
@@ -36,7 +40,13 @@ class ImplementsIdentifiable<ID> extends Identified<ID> {
 
 abstract class Permissible {
     static readonly defaultPermissions: string[] = []
-    permissions: string[] = []
+    // permissions: string[] = []
+    permissions!: string[]
+
+    initializer() {
+        console.log("Permissible initializer")
+        this.permissions = []
+    }
 }
 
 
@@ -55,11 +65,11 @@ class User extends expresses(
 
 console.log(new User(BigInt(1)))
 
-// console.log(Permissible.constructor())
+console.log(Permissible.constructor())
-// console.log(Object.getOwnPropertyNames(User.prototype))
+console.log(Object.getOwnPropertyNames(User.prototype))
 
-// const user1 = new User(BigInt(1))
+const user1 = new User(BigInt(1))
-// const user2 = new User(BigInt(2))
+const user2 = new User(BigInt(2))
 
-// console.log(user1.equals(user2))
+console.log(user1.equals(user2))
-// console.log(user1.permissions)
+console.log(user1.permissions)

src/trait.ts

@@ -1,72 +1,85 @@
 import { AbstractClass, Class, UnionToIntersection } from "type-fest"
-import { StaticMembers, copyProperties, flattenClass, getInheritanceHierarchy } from "./util/class"
+import { StaticMembers, copyProperties, getInheritanceHierarchy } from "./util/class"
 
 
+/**
+ * Represents a trait that can be used to define common behavior
+ * for classes and abstract classes.
+ * @typeParam T - The type of the trait.
+ */
 export type Trait<T> =
     AbstractClass<T, []>
 
 
-// export function applyTrait<
+/**
-//     C      extends Class<any, any> | AbstractClass<any, any>,
+ * Creates a link class that expresses the given traits.
-//     TraitC extends Trait<any>,
+ * @param traits - An array of traits to be expressed by the link class.
-// >(
+ * @returns A dynamically created class that expresses the given traits.
-//     class_:  C,
+ * @typeParam Traits - An array of traits that the link class expresses.
-//     trait:   TraitC,
+ */
-// ) {
-//     copyClassProperties(trait, class_)
-
-//     return class_ as (
-//         (C extends Class<any, any>
-//             ? Class<
-//                 InstanceType<C> & InstanceType<TraitC>,
-//                 ConstructorParameters<C>
-//             >
-//             : AbstractClass<
-//                 InstanceType<C> & InstanceType<TraitC>,
-//                 ConstructorParameters<C>
-//             >
-//         ) &
-//         StaticMembers<C> &
-//         StaticMembers<TraitC>
-//     )
-// }
-
-
-export const extendAndApplyTraits = <
-    C      extends Class<any, any> | AbstractClass<any, any>,
-    Traits extends readonly Trait<any>[],
->(
-    classToExtend:  C,
-    traits:         Traits,
-) =>
-    traits.reduce((class_, trait) => {
-        copyProperties(flattenClass(trait), class_)
-        return class_
-    }, class extends classToExtend {}) as (
-        AbstractClass<
-            InstanceType<C> &
-            UnionToIntersection<
-                InstanceType<Traits[number]>
-            >,
-
-            ConstructorParameters<C>
-        > &
-
-        StaticMembers<
-            C &
-            UnionToIntersection<
-                Traits[number]
-            >
-        >
-    )
-
-
 export function expresses<
     Traits extends readonly Trait<any>[]
 >(
     ...traits: Traits
 ) {
-    const class_ = class {}
+    return makeLinkClass(traits)
+}
+
+
+/**
+ * Creates a link class that extends a base class and expresses the given traits.
+ * @param extend - The base class or abstract class to extend.
+ * @param traits - An array of traits to be expressed by the link class.
+ * @returns A dynamically created class that extends the given base class and expresses the given traits.
+ * @typeParam C - The type of the base class to extend.
+ * @typeParam Traits - An array of traits that the link class expresses.
+ */
+export function extendsAndExpresses<
+    C      extends Class<any, any>
+                 | AbstractClass<any, any>,
+    Traits extends readonly Trait<any>[],
+>(
+    extend:     C,
+    ...traits:  Traits
+) {
+    return makeLinkClass(traits, extend)
+}
+
+
+/**
+ * Creates a link class that expresses the given traits and optionally extends a base class.
+ * @param traits - An array of traits to be expressed by the link class.
+ * @param extend - The base class or abstract class to extend (optional).
+ * @returns A dynamically created class that expresses the given traits and extends the base class.
+ * @typeParam Traits - An array of traits that the link class expresses.
+ * @typeParam C - The type of the base class to extend (optional).
+ */
+export function makeLinkClass<
+    Traits extends readonly Trait<any>[],
+    C      extends Class<any, any>
+                 | AbstractClass<any, any>
+                 | undefined = undefined,
+>(
+    traits:   Traits,
+    extend?:  C,
+) {
+    const class_ = extend
+        ? class extends extend {
+            constructor(...args: any[]) {
+                super(...args)
+
+                traits.forEach(trait => {
+                    trait.prototype.initializer?.call(this)
+                })
+            }
+        }
+        : class {
+            constructor() {
+                traits.forEach(trait => {
+                    trait.prototype.initializer?.call(this)
+                })
+            }
+        }
 
     traits.forEach(trait => {
         getInheritanceHierarchy(trait).forEach(current => {
@@ -80,13 +93,29 @@ export function expresses<
     })
 
     return class_ as unknown as (
-        Trait<
+        (C extends Class<any, any> | AbstractClass<any, any>
-            UnionToIntersection<
+            ? (
-                InstanceType<
+                AbstractClass<
-                    Traits[number]
+                    InstanceType<C> &
+                    UnionToIntersection<
+                        InstanceType<
+                            Traits[number]
+                        >
+                    >,
+
+                    ConstructorParameters<C>
+                > &
+
+                StaticMembers<C>
+            )
+            : Trait<
+                UnionToIntersection<
+                    InstanceType<
+                        Traits[number]
+                    >
                 >
             >
-        > &
+        ) &
 
         StaticMembers<
             UnionToIntersection<