README
class-transformer-validator-light
A simple plugin for class-transformer and class-validator-light which combines them in a nice and programmer-friendly API.
Installation
Module installation
npm install @servrox/class-transformer-validator-light --save
(or the short way):
npm i -S @servrox/class-transformer-validator-light
Peer dependencies
This package is only a simple plugin/wrapper, so you have to install the required modules too because it can't work without them. See detailed installation instruction for the modules installation:
Usage
The usage of this module is very simple.
import { IsEmail } from "@servrox/class-validator-light";
import { transformAndValidate } from "@servrox/class-transformer-validator-light";
// declare the class using class-validator decorators
class User {
@IsEmail()
public email: string;
public hello(): string {
return "World!";
}
}
// then load the JSON string from any part of your app
const userJson: string = loadJsonFromSomething();
// transform the JSON to class instance and validate it correctness
transformAndValidate(User, userJson)
.then((userObject: User) => {
// now you can access all your class prototype method
console.log(`Hello ${userObject.hello()}`); // prints "Hello World!" on console
})
.catch(err => {
// here you can handle error on transformation (invalid JSON)
// or validation error (e.g. invalid email property)
console.error(err);
});
You can also transform and validate plain JS object (e.g. from express req.body). Using ES7 async/await syntax:
async (req, res) => {
try {
// transform and validate request body
const userObject = await transformAndValidate(User, req.body);
// infered type of userObject is User, you can access all class prototype properties and methods
} catch (err) {
// your error handling
console.error(err);
}
};
And since release 0.3.0
you can also pass array of objects - all of them will be validated using given class validation constraints:
async (req, res) => {
try {
// transform and validate request body - array of User objects
const userObjects = await transformAndValidate(User, req.body);
userObjects.forEach(user => console.log(`Hello ${user.hello()}`));
} catch (err) {
// your error handling
}
};
API reference
Function signatures
There is available the transformAndValidate
function with three overloads:
function transformAndValidate<T extends object>(
classType: ClassType<T>,
jsonString: string,
options?: TransformValidationOptions,
): Promise<T | T[]>;
function transformAndValidate<T extends object>(
classType: ClassType<T>,
object: object,
options?: TransformValidationOptions,
): Promise<T>;
function transformAndValidate<T extends object>(
classType: ClassType<T>,
array: object[],
options?: TransformValidationOptions,
): Promise<T[]>;
Be aware that if you validate json string, the return type is a Promise
of T
or T[]
so you need to assert the returned type if you know the shape of json:
const users = (await transformAndValidate(
User,
JSON.stringify([{ email: "test@test.test" }]),
)) as User[];
Or you can just check the type in runtime using Array.isArray
method.
Synchronous transformation and validation
If you need sync validation, use transformAndValidateSync
function instead (available since v0.4.0). It will synchronously return T
or T[]
, not a Promise.
Parameters and types
classType
- an class symbol, a constructor function which can be called withnew
type ClassType<T> = {
new (...args: any[]): T;
};
jsonString
- a normal string containing JSONobject
- plain JS object of typeobject
(introduced in TypeScript 2.2), you will have compile-time error while trying to pass number, boolean, null or undefined but unfortunately run-time error when passing a functionarray
- array of plain JS objects like described aboveoptions
- optional options object, it has two optional properties
interface TransformValidationOptions {
validator?: ValidatorOptions;
transformer?: ClassTransformOptions;
}
You can use it to pass options for class-validator
(more info) and for class-transformer
(more info).
More info
The class-transformer and class-validator are more powerfull than it was showed in the simple usage sample, so go to their github page and check out they capabilities!
Release notes
0.8.0
- updated
class-transformer
dependency to version^0.2.3
- updated
class-validator
dependency to version^0.10.1
- updated TypeScript dependency to version
^3.6.3
- built code is now emitted as ES2015 (dropped es5 support)
- updated all dev dependencies
0.7.1
- updated
class-transformer
dependency to version^0.2.0
0.6.0
- updated
class-validator
dependency to version^0.9.1
0.5.0
- remove deprecated
TransformValdiationOptions
interface (typo) - updated
class-validator
dependency to version^0.8.1
andclass-transformer
to^0.1.9
0.4.1
- fix
TransformValdiationOptions
interface name typo (deprecate in favour ofTransformValidationOptions
)
0.4.0
- added
transformAndValidateSync
function for synchronous validation - changed return type for JSON's transform and validation to
Promise
ofT
orT[]
- updated
class-validator
dependency to version^0.7.2
andclass-transformer
to^0.1.7
0.3.0
- added support for transform and validate array of objects given class
- updated
class-validator
dependency to version^0.7.1
0.2.0
- changed object parameter type declaration to
object
(introduced in TS 2.2) - throwing error when passed array, undefined or null
0.1.1
- changed throwing error (rejecting promise) from string to
Error
with message
0.1.0
- initial version with
transformAndValidate
function