Function: Expect()

Expect<ClassPrototype>(schema): PropertyDecorator<ClassPrototype>

Declare the schema of a property of a DTO class. The DTO validates the property against it when it is constructed (the whole object at once: defaults applied, the keys without schema removed unless the class has an @IndexSignature), and each time the property, or a value nested in it, is changed afterwards (the change is undone when invalid). The schema is also part of the class schema (MyDTO.Schema()) used by @Accept, @Return and the actions' input validation. Subclasses inherit the property schemas, and may declare a property again to replace its schema. Ignored on a symbol property or on a class which is not a DTO.

Type Parameters

ClassPrototype

ClassPrototype extends DTO

Parameters

schema

Schema

The schema of the property, built with the static methods of DTO (DTO.String().required()); a property is optional unless its schema is marked required().

Returns

PropertyDecorator<ClassPrototype>

The property decorator.

Throws

From the DTO constructor, or from an assignment to the property, when the value does not match the schema.

Example

import {DTO} from 'lakutata'
import {Expect} from 'lakutata/decorator/dto'

class CreateUserDTO extends DTO {
    @Expect(DTO.String().min(2).max(50).required())
    public name!: string

    @Expect(DTO.String().email().required())
    public email!: string

    @Expect(DTO.Number().integer().min(0).optional().default(0))
    public credits?: number
}

//Validated when constructed: credits is 0, an invalid email throws an InvalidValueException
const user: CreateUserDTO = new CreateUserDTO({name: 'Ada', email: 'ada@example.com'})
//Validated when changed: throws an InvalidValueException, the name is unchanged
user.name = 'A'