auto_mappr 1.0.0

Mapping between different objects with ease

AutoMappr

Developed with 💚 by netglade

---

A mapper that maps between different objects with ease. Heavily inspired by C# AutoMapper.

Thanks to code generation, you can generate AutoMappr classes, which will allow mapping between different objects automatically without the need to write these mapping by hand.

• 🚀 Getting started
  • How to use
  • Install
  • Run the generator
• ✨ Features
  • ✅ Primitive objects mapping
  • ✅ Complex objects mapping
  • ✅ Field mapping
  • ✅ Custom mapping
  • ✅ Ignore mapping
  • ✅ List-like objects mapping
  • ✅ Map objects mapping
  • ✅ Default field value
  • ✅ Default object value
  • ✅ Constructor selection
  • ✅ Positional and named constructor parameters
  • ✅ Mapping to target
  • ✅ Mapping from source
  • ✅ Nullability handling
  • ✅ Works with equatable
  • ✅ Works with json_serializable
• ⚙️ Customizing the build
• 👏 Contributing

🚀 Getting started

How to use

Create a mapping class with @AutoMappr annotation. You will also need to import the annotation.

import 'package:auto_mappr_annotation/auto_mappr_annotation.dart';

part 'my_file.g.dart';

@AutoMappr([
  MapType<UserDto, User>(
    fields: [
      Field('name', target: Mappr.mapName),
      Field('age', target: mapAge),
      Field('tag', ignore: true)
    ],
  ),
])
class Mappr extends $Mappr {
  static String mapName(UserDto dto) => dto.name.toUpperCase();
}

int mapAge(UserDto _) => 55;

Install

To use AutoMappr, install these three packages:

• build_runner -- the tool to run code-generators
• auto_mappr -- the AutoMappr code generator
• auto_mappr_annotation -- the AutoMappr annotation

For a Flutter project:

flutter pub add auto_mappr_annotation
flutter pub add --dev build_runner
flutter pub add --dev auto_mappr

For a Dart project:

dart pub add auto_mappr_annotation
dart pub add --dev build_runner
dart pub add --dev auto_mappr

Run the generator

For a Flutter project:

flutter pub run build_runner build

For a Dart project:

dart run build_runner build

✨ Features

Primitive objects mapping

Primitive objects like num, int, double, String, bool, Symbol, Type, and null are copied to target object with no additional processing.

Complex objects mapping

Complex (or nested) objects are mapped according to their MapType<SOURCE, TARGET>() mapping setup. The generator generates mapping methods for each MapType. These mapping methods are used in nested objects.

Field mapping

When target and source fields' name do not match, you can change source field by using the from argument in a Field() mapping. Alternatively, you can use the Field.from() constructor which hides other then-invalid parameters.

@AutoMappr([
  MapType<UserDto, User>(
    fields: [
      Field('name', from: 'myName'),
      Field.from('age', from: 'myAge'),
    ],
  ),
])
class Mappr extends $Mappr {}

Custom mapping

When you need to assign a custom function or a const value as a value for given target field, you can use the custom argument in a Field mapping. Alternatively, you can use the Field.custom() constructor which hides other then-invalid parameters.

You can set up Target Function(Source dto) function or const Target value.

@AutoMappr([
  MapType<UserDto, User>(
    fields: [
      Field('name', custom: Mappr.mapName), // Static Mappr method.
      Field('age', custom: mapAge), // Global method.
      Field.custom('note', custom: 'constant value'), // Constant value.
    ],
  ),
])
class Mappr extends $Mappr {
  static String mapName(UserDto dto) => dto.name.toUpperCase();
}

int mapAge(UserDto _) => 42;

Ignore mapping

To completely ignore some target field, so it is not mapped into a constructor or into a setter, you can use the ignore argument in a Field mapping. Alternatively, you can use the Field.ignore() constructor which hides other then-invalid parameters.

@AutoMappr([
  MapType<UserDto, User>(
    fields: [
      Field('name', ignore: true),
      Field.ignore('age', ignore: true),
    ],
  ),
])
class Mappr extends $Mappr {}

List-like objects mapping

Values in list-like collections like List, Set, or Iterable are mapped using the .map() method when the values are complex types. When needed, mostly after mapping, .toList() or .toSet() methods are called to cast an Iterable into a List/Set.

Map objects mapping

Maps are a specific case of Iterables, that has to be handled a bit differently. For example, we must make sure that both keys and values of MapEntry are mapped correctly based on whether they are primitive or complex types.

Default field value

To make sure that a default value is assigned to a target field when a source field is null you can set up a whenNull property on Field which takes a constant value of target field type.

You can set up default field value by using Target Function() function or const Target value on Field, Field.from, and Field.custom, constructors but not on Field.ignore constructor.

@AutoMappr([
  MapType<UserDto, User>(
    fields: [
      Field('name', whenNull: 'John Smith'),
    ],
  ),
])
class Mappr extends $Mappr {}

Default object value

When the whole source object is null, you can set up a default value for it using the whenSourceIsNull property on MapType. It can also take a constant value of target object type.

You can set up Target Function() function or const Target value.

@AutoMappr([
  MapType<UserDto, User>(
    whenSourceIsNull: User(name: 'Neo', age: 28),
  ),
])
class Mappr extends $Mappr {}

Constructor selection

The mapping automatically selects a constructor with the most parameters. When you want to specifically select a certain constructor, set the constructor property on MapType.

Imagine that you have a User(String name, int age, String note) and User.fromDto(String name, int age) constructors. Default algorithm selects the default constructor because it has the most parameters. To change the selected constructor, do:

@AutoMappr([
  MapType<UserDto, User>(
    constructor: 'fromDto',
  ),
])
class Mappr extends $Mappr {}

Positional and named constructor parameters

The mapping automatically assigns source getters to constructor parameters no matter if they are positional or named.

Mapping to target

Mapping into a target object can be done in two places. First, the mapping tries to map all the fields to selected constructor. And for the target fields that have not been mapped, it tries to set them using public setters (both explicit ones or implicit ones created by fields), if they have any.

Mapping from source

Mapping from a source object can be done from either public getters or static getters. Getters can be both explicit ones or implicit ones created by fields.

Nullability handling

For each MapType<SOURCE, TARGET>() mapping the generator generates at most two mapping methods. First method is a method with non-nullable return type TARGET. Second method is a method with nullable return type TARGET? that is being generated only when other methods use it. If the object mapping has whenSourceIsNull parameter set, the nullable method is not generated.

Note that convert cannot return null. The value null can only be returned for nested object mappings.

Works with equatable

Mapping works with the Equatable package. Some mapping tools tries to map the props getter, but since AutoMappr maps only to public explicit or implicit setters, Equatable and other packages with similar conditions implicitly works.

Works with json_serializable

AutoMappr uses a SharedPartBuilder. That means it can share the .g.dart file with packages like JSON Serializable to generate other code to the generated super class.

⚙ Customizing the build

By default, AutoMappr uses the auto_mappr:auto_mappr builder that works with SharedPartBuilder, which generates combined .g.dart files. If you need to use PartBuilder to generate not-shared .auto_mappr.dart part files, you can use the auto_mappr:not_shared builder.

Modify your build.yaml file:

targets:
  $default:
    # You can disable all default builders.
    auto_apply_builders: false
    builders:
      # Or disable specific ones.
      auto_mappr:
        enabled: false
      # And enable the not_shared builder.
      auto_mappr:not_shared:
        enabled: true

If you are using packages like Drift which generates classes you need to use as a source or a target in your mappings, use their not-shared builder, if they have any. With that, the builder can generate files like .drift.dart which you can add a input dependency to. Specify the required_inputs dependency on your local AutoMappr builder and disable the builders provided by AutoMappr.

Shared builder:

targets:
  $default:
    # Disable the default generators (or disable the default builders you don't want to use).
    auto_apply_builders: false
    builders:
      # Enable their generators according to their documentation.
      drift_dev:not_shared:
        enabled: true
      drift_dev:preparing_builder:
        enabled: true
      # Enable local shared AutoMappr builder defined below.
      :auto_mappr:
        enabled: true

# Local builders.
builders:
  auto_mappr:
    required_inputs: [".drift.dart"] # <-- here are your dependencies
    import: "package:auto_mappr/builder.dart"
    builder_factories: ["autoMapprBuilder"]
    build_extensions: { ".dart": [".auto_mappr.g.part"] }
    auto_apply: none
    build_to: cache
    applies_builders: ["source_gen:combining_builder"]

Not shared builder:

targets:
  $default:
    # Disable the default generators (or disable the default builders you don't want to use).
    auto_apply_builders: false
    builders:
      # Enable their generators according to their documentation.
      drift_dev:not_shared:
        enabled: true
      drift_dev:preparing_builder:
        enabled: true
      # Enable local not-shared AutoMappr builder defined below.
      :auto_mappr:not_shared:
        enabled: true

# Local builders.
builders:
  not_shared:
    required_inputs: [".drift.dart"] # <-- here are your dependencies
    import: "package:auto_mappr/builder.dart"
    builder_factories: ["autoMapprBuilderNotShared"]
    build_extensions: { ".dart": ["auto_mappr.dart"] }
    auto_apply: none
    build_to: source

👏 Contributing

Your contributions are always welcome! Feel free to open pull request.