Overview

Convention over Configuration

AutoMapper does have Auto in its name. If we follow closely Conventions, we rarely need MappingConfiguration.

As we have already seen in previous examples, matching properties are mapped automatically as long as the metadata is provided.

class User {
    @AutoMap()
    firstName!: string;
    @AutoMap()
    lastName!: string;
}

class UserDto {
    @AutoMap()
    firstName!: string;
    @AutoMap()
    lastName!: string;
}

Nested models are also auto-mapped.

class Address {
    @AutoMap()
    street!: string;
}

class Bio {
    @AutoMap()
    text!: string;
    @AutoMap(() => [Address])
    addresses: Address[] = [];
}

class User {
    @AutoMap(() => Bio)
    bio!: Bio;
}

class AddressDto {
    @AutoMap()
    street!: string;
}

class BioDto {
    @AutoMap()
    text!: string;
    @AutoMap(() => [AddressDto])
    addresses: AddressDto[] = [];
}

class UserDto {
    @AutoMap(() => BioDto)
    bio!: BioDto;
}

In addition, there is Auto Flattening. These features should encourage us to stay as close to the conventions as possible.

Custom Configuration

MappingConfiguration are functions that augment a Mapping. When creating a Mapping with createMap(), we can pass in as many MappingConfiguration as we like and in any order that we want.

mapping configuration	description
afterMap()	Attach a MapCallback to run after the map operation
beforeMap()	Attach a MapCallback to run before the map operation
constructUsing()	Set a custom constructor for the Destination before the map operation
extend()	Extend another Mapping
forMember()	Configure a MappingTransformation for a property on the Destination
forSelf()	Configure flattening for Destination from a different Source
namingConventions()	Configure the NamingConvention for this Mapping
typeConverters()	Configure the TypeConverter for this Mapping

caution

If the Mapping have an absurd amount of custom MappingConfiguration, it's time to re-evaluate the models or if AutoMapper is the right tool for the project.