extend type use TS declaration merge feature

CHANGELOG.md

@@ -1,3 +1,8 @@
+## 1.10.0
+
+- new way to extend type to a class: `Model`
+- deprecates the old way `extend`
+
 ## 1.9.0
 
 - supports `enumSchema`

README.md

@@ -210,7 +210,7 @@ const iGuest = decoder.decode<IGuest>('IGuest', data);
 const guest = new Guest(iGuest);
 ```
 
-You may use the `extend` function to extend the interface:
+You may subclass `Model<T>` to extend the interface:
 
 ```typescript
 import { extend } from 'io-interface';
@@ -220,54 +220,24 @@ interface IUser {
   lastName: string;
 }
 
-const User = extend<IUser>()(user => ({
+interface User extends IUser {}
+class User {
   get name(): string {
     return `${user.firstName} ${user.lastName}`;
   },
-}));
-
-type User = InstanceType<typeof User>;
+}
 
 decoder.register({
   schema: schema<IUser>(),
-  constructor: User, // matches "const User"
-  className: 'User', // matches name of "type User"
+  constructor: User,
+  className: 'User',
 });
 
 const user = decoder.decode<User>('User', { firstName: 'Yang', lastName: 'Liu' });
 
 console.log(user.name);
 ```
 
-#### Extended constructors are composible
-
-You can use a registered extended type as a field of other interface.
-
-```typescript
-interface ICompany {
-  user: User; // use a registed extended type here
-  name: string;
-}
-const Company = extend<ICompany>()(c => ({
-  get boss(): string {
-    return c.user.name;
-  },
-}));
-type Company = InstanceType<typeof Company>;
-
-// register company
-
-const json = {
-  name: 'Good Inc',
-  user: {
-    firstName: 'Yang',
-    lastName: 'Liu',
-  },
-};
-
-const company = decoder.decode<Company>('Company', json);
-```
-
 ## Installation
 
 ### Setup ts-patch
@@ -432,7 +402,7 @@ class ApiService {
     options: ApiOptions,
     cb: (c: Decoder, data: unknown, e?: DecoderCallback<T>) => T | undefined,
   ) {
-    const data: Object = await fecth(options);
+    const data: Object = await fetch(options);
     const casted: T = cb(c, data, console.error);
     return casted;
   }

index.ts

@@ -120,6 +120,7 @@ export type Builder = ClassBuilder | CasterBuilder;
 
 /**
  * Extends type T with mixin U.
+ * @deprecated use Model<T> instead
  * @since 1.6.0
  * @example
  * interface IUser {
@@ -146,6 +147,24 @@ export function extend<T extends object>() {
   };
 }
 
+/**
+ * Allow constructing from a plain object.
+ * @since 1.10.0
+ * @example
+ * interface IUser { name: string; }
+ * interface User extends IUser {}
+ * class User extends Model<IUser> {
+ *   get title() {
+ *     return `Dr. ${this.name}`;
+ *   }
+ * }
+ */
+export class Model<T> {
+  constructor(data: T) {
+    Object.assign(this, data);
+  }
+}
+
 function isClassBuilder(o: any): o is ClassBuilder {
   return ['schema', 'className', 'constructor'].every(k => k in o);
 }

test/sample.ts

@@ -1,4 +1,4 @@
-import { Decoder, runtime, schema, extend, enumSchema } from '..';
+import { Decoder, runtime, schema, extend, enumSchema, Model } from '..';
 import { casters, Latitude, Longitude, Int, NonEmptyString } from '../types';
 import * as t from 'io-ts';
 
@@ -372,13 +372,19 @@ interface ICustomer {
   lastName: string;
 }
 
-const Customer = extend<ICustomer>()(cus => ({
-  get fullName(): string {
-    return `${cus.firstName} ${cus.lastName}`;
-  },
-}));
+// const Customer = extend<ICustomer>()(cus => ({
+//   get fullName(): string {
+//     return `${cus.firstName} ${cus.lastName}`;
+//   },
+// }));
 
-type Customer = InstanceType<typeof Customer>;
+// type Customer = InstanceType<typeof Customer>;
+interface Customer extends ICustomer {}
+class Customer extends Model<ICustomer> {
+  get fullName(): string {
+    return `${this.firstName} ${this.lastName}`;
+  }
+}
 
 dec.register({
   schema: schema<ICustomer>(),
@@ -394,6 +400,7 @@ const cus: Customer | undefined = dec.decode('Customer', good15, e => {
 
 if (cus) {
   console.log('extend function:', JSON.stringify(cus, null, 2));
+  console.log('extend function: get fullName():', cus.fullName);
 } else {
   throw new Error('extend function NOT WORKING!!!');
 }
@@ -407,13 +414,12 @@ interface ICompany {
   customer: Customer;
 }
 
-const Company = extend<ICompany>()(c => ({
+interface Company extends ICompany {}
+class Company extends Model<ICompany> {
   get boss(): string {
-    return c.name;
-  },
-}));
-
-type Company = InstanceType<typeof Company>;
+    return this.name;
+  }
+}
 
 dec.register({
   schema: schema<ICompany>(),
@@ -433,7 +439,7 @@ const company: Company | undefined = dec.decode<Company>('Company', good37, e =>
   throw e;
 });
 if (company) {
-  console.log('nested constructor passed', company);
+  console.log('nested constructor passed', JSON.stringify(company, null, 2));
 } else {
   throw new Error('nested constructor NOT WORKING!!!');
 }
@@ -537,12 +543,12 @@ test('enumSchema error example', 'OrderStatus', st2, false);
 interface IDay {
   date: Date | null;
 }
-const Day = extend<IDay>()(d => ({
+interface Day extends IDay {}
+class Day extends Model<IDay> {
   get d() {
-    return d.date;
-  },
-}));
-type Day = InstanceType<typeof Day>;
+    return this.date;
+  }
+}
 
 dec.register({
   schema: schema<IDay>(),