feat(decorator): add plainToClass decorator

Author: snirs90

src/decorators.ts

@@ -86,4 +86,22 @@ export function TransformClassToClass(params?: ClassTransformOptions): Function
             return isPromise ? result.then((data: any) => classTransformer.classToClass(data, params)) : classTransformer.classToClass(result, params);
         };
     };
+}
+
+/**
+ * Return the class instance only with the exposed properties.
+ */
+export function TransformPlainToClass(classType: any, params?: ClassTransformOptions): Function {
+
+    return function (target: Function, propertyKey: string, descriptor: PropertyDescriptor) {
+        const classTransformer: ClassTransformer = new ClassTransformer();
+        const originalMethod = descriptor.value;
+
+        descriptor.value = function(...args: any[]) {
+            const result: any = originalMethod.apply(this, args);
+            const isPromise = !!result && (typeof result === "object" || typeof result === "function") && typeof result.then === "function";
+
+            return isPromise ? result.then((data: any) => classTransformer.plainToClass(classType, data, params)) : classTransformer.plainToClass(classType, result, params);
+        };
+    };
 }

test/functional/transformer-method.spec.ts

@@ -1,6 +1,6 @@
 import "reflect-metadata";
 import {defaultMetadataStorage} from "../../src/storage";
-import {Exclude, Expose, TransformClassToPlain, TransformClassToClass} from "../../src/decorators";
+import { Exclude, Expose, TransformClassToPlain, TransformClassToClass, TransformPlainToClass } from "../../src/decorators";
 import {expect} from "chai";
 
 describe("transformer methods decorator", () => {
@@ -50,6 +50,49 @@ describe("transformer methods decorator", () => {
         expect(result).to.be.instanceof(User);
     });
 
+    it("should expose non configuration properties and return User instance class instead of plain object", () => {
+        defaultMetadataStorage.clear();
+
+        @Exclude()
+        class User {
+
+            id: number;
+
+            @Expose()
+            firstName: string;
+
+            @Expose()
+            lastName: string;
+
+            password: string;
+        }
+
+        class UserController {
+
+            @TransformPlainToClass(User)
+            getUser() {
+                const user: any = {};
+                user.firstName = "Snir";
+                user.lastName = "Segal";
+                user.password = "imnosuperman";
+
+                return user;
+            }
+        }
+
+        const controller = new UserController();
+
+        const result = controller.getUser();
+        expect(result.password).to.be.undefined;
+
+        const user = new User();
+        user.firstName = "Snir";
+        user.lastName = "Segal";
+
+        expect(result).to.be.eql(user);
+        expect(result).to.be.instanceof(User);
+    });
+
     it("should expose non configuration properties", () => {
         defaultMetadataStorage.clear();