Serialization
Source-generated serialization for Dart objects. This package uses
package:source_gen to eliminate the time you spend writing boilerplate serialization code for your models. package:angel3_serialize also powers package:angel3_orm.In your
pubspec.yaml, you need to install the following dependencies:dependencies:
angel3_model: ^3.0.0
angel3_serialize: ^4.0.0
dev_dependencies:
angel3_serialize_generator: ^4.2.0
build_runner: ^1.0.0
With the recent updates to
package:build_runner, you can build models automatically, anywhere in your project structure, by running pub run build_runner build.If you want to watch for file changes and re-build when necessary, replace the
build call with a call to watch. They take the same parameters.There are a few changes opposed to normal Model classes. You need to add a
@serializable annotation to your model class to have it serialized, and a serializable model class's name should also start with a leading underscore.In addition, you may consider using an
abstract class to ensure immutability of models.Rather you writing the public class,
angel3_serialize does it for you. This means that the main class can have its constructors automatically generated, in addition into serialization functions.For example, say we have a
Book model. Create a class named _Book:import 'package:angel3_model/angel_model.dart';
import 'package:angel3_serialize/angel3_serialize.dart';
import 'package:collection/collection.dart';
part 'book.g.dart';
@serializable
abstract class _Book extends Model {
String get author;
@SerializableField(defaultValue: '[Untitled]')
String get title;
String get description;
int get pageCount;
BookType get type;
}
/// It even supports enums!
enum BookType {
fiction,
nonFiction
}
The following file will be generated:
book.g.dart
Producing these classes:
Book: Extends or implements_Book; may beconst-enabled.BookSerializer: static functionality for serializingBookmodels.BookFields: The names of all fields from theBookmodel, statically-available.BookEncoder: AllowsBookSerializerto extendCodec<Book, Map>.BookDecoder: Also allowsBookSerializerto extendCodec<Book, Map>.
And the following other features:
bookSerializer: A top-level,constinstance ofBookSerializer.Book.toString: Prints out all of aBookinstance's fields.
You can use the generated files as follows:
myFunction() {
var warAndPeace = new Book(
author: 'Leo Tolstoy',
title: 'War and Peace',
description: 'You will cry after reading this.',
pageCount: 1225
);
// Easily serialize models into Maps
var map = BookSerializer.toMap(warAndPeace);
// Also deserialize from Maps
var book = BookSerializer.fromMap(map);
print(book.title); // 'War and Peace'
// For compatibility with `JSON.encode`, a `toJson` method
// is included that forwards to `BookSerializer.toMap`:
expect(book.toJson(), map);
// Generated classes act as value types, and thus can be compared.
expect(BookSerializer.fromMap(map), equals(warAndPeace));
}
As of
2.0.2, the generated output also includes information about the serialized names of keys on your model class. myOtherFunction() {
// Relying on the serialized key of a field? No worries.
map[BookFields.author] = 'Zora Neale Hurston';
}
Currently, these serialization methods are supported:
- to
Map - to JSON
- to TypeScript definitions
You can customize these by means of
serializers:@Serializable(serializers: const [Serializers.map, Serializers.json])
class _MyClass extends Model {}
angel3_serialize pulls in fields from parent classes, as well as implemented interfaces, so it is extremely easy to share attributes among model classes:import 'package:angel3_serialize/angel3_serialize.dart';
part 'subclass.g.dart';
@serializable
class _Animal {
@notNull
String genus;
@notNull
String species;
}
@serializable
class _Bird extends _Animal {
@DefaultsTo(false)
bool isSparrow;
}
var saxaulSparrow = Bird(
genus: 'Passer',
species: 'ammodendri',
isSparrow: true,
);
Whereas Dart fields conventionally are camelCased, most database columns tend to be snake_cased. This is not a problem, because we can define an alias for a field.
By default
angel3_serialize will transform keys into snake case. Use alias to provide a custom name, or pass autoSnakeCaseNames: false to the builder;@serializable
abstract class _Spy extends Model {
/// Will show up as 'agency_id' in serialized JSON.
///
/// When deserializing JSON, instead of searching for an 'agencyId' key,
/// it will use 'agency_id'.
///
/// Hooray!
String agencyId;
@SerializableField(alias: 'foo')
String someOtherField;
}
You can also override
autoSnakeCaseNames per model:@Serializable(autoSnakeCaseNames: false)
abstract class _OtherCasing extends Model {
String camelCasedField;
}
In pratice, there may keys that you want to exclude from JSON. To accomplish this, simply annotate them with
@exclude:@serializable
abstract class _Whisper extends Model {
/// Will never be serialized to JSON
@SerializableField(exclude: true)
String secret;
}
There are times, however, when you want to only exclude either serialization or deserialization, but not both. For example, you might want to deserialize passwords from a database without sending them to users as JSON.
In this case, use
canSerialize or canDeserialize:@serializable
abstract class _Whisper extends Model {
/// Will never be serialized to JSON
///
/// ... But it can be deserialized
@SerializableField(exclude: true, canDeserialize: true)
String secret;
}
It is easy to mark a field as required:
@serializable
abstract class _Foo extends Model {
@SerializableField(isNullable: false)
int myRequiredInt;
@SerializableField(isNullable: false, errorMessage: 'Custom message')
int myOtherRequiredInt;
}
The given field will be marked as
@required in the generated constructor, and serializers will check for its presence, throwing a FormatException if it is missing.There are times when you need the generated class to have annotations affixed to it:
@Serializable(
includeAnnotations: [
Deprecated('blah blah blah'),
pragma('something...'),
]
)
abstract class _Foo extends Model {}
package:angel3_serialize does not cover every known Dart data type; you can add support for your own. Provide serializer and deserializer arguments to @SerializableField() as you see fit.They are typically used together. Note that the argument to
deserializer will always be dynamic, while serializer can receive the data type in question.In such a case, you might want to also provide a
serializesTo argument. This lets the generator, as well as the ORM, apply the correct (de)serialization rules and validations.DateTime _dateFromString(s) => s is String ? HttpDate.parse(s) : null;
String _dateToString(DateTime v) => v == null ? null : HttpDate.format(v);
@serializable
abstract class _HttpRequest {
@SerializableField(
serializer: #_dateToString,
deserializer: #_dateFromString,
serializesTo: String)
DateTime date;
}
angel3_serialize also supports a few types of nesting of @serializable classes:- As a class member, ex.
Book myField - As the type argument to a
List, ex.List<Book> - As the second type argument to a
Map, ex.Map<String, Book>
In other words, the following are all legal, and will be serialized/deserialized. You can use either the underscored name of a child class (ex.
_Book), or the generated class name (ex Book):@serializable
abstract class _Author extends Model {
List<Book> books;
Book newestBook;
Map<String, Book> booksByIsbn;
}
If your model (
Author) depends on a model defined in another file (Book), then you will need to generate book.g.dart before, author.g.dart, in a separate build action. This way, the analyzer can resolve the Book type.This package will automatically generate
id, createdAt, and updatedAt fields for you, in the style of an Angel3 Model. This will automatically be generated, only for classes extending Model.package:angel3_serialize also handles Uint8List fields, by means of serialization to and from base64 encoding.It is quite common to build frontends with JavaScript and/or TypeScript, so why not generate typings as well?
To accomplish this, add
Serializers.typescript to your @Serializable() declaration:@Serializable(serializers: const [Serializers.map, Serializers.json, Serializers.typescript])
class _Foo extends Model {}
The aforementioned
_Author class will generate the following in author.d.ts:interface Author {
id: string;
name: string;
age: number;
books: Book[];
newest_book: Book;
created_at: any;
updated_at: any;
}
interface Library {
id: string;
collection: BookCollection;
created_at: any;
updated_at: any;
}
interface BookCollection {
[key: string]: Book;
}
Fields with an
@Exclude() that specifies canSerialize: false will not be present in the TypeScript definition. The rationale for this is that if a field (i.e. password) will never be sent to the client, the client shouldn't even know the field exists.Sometimes, you may need to have custom constructor parameters, for example, when using depedency injection frameworks. For these cases,
angel3_serialize can forward custom constructor parameters.The following:
@serializable
abstract class _Bookmark extends _BookmarkBase {
@SerializableField(exclude: true)
final Book book;
int get page;
String get comment;
_Bookmark(this.book);
}
Generates:
class Bookmark extends _Bookmark {
Bookmark(Book book,
{this.id,
this.page,
this.comment,
this.createdAt,
this.updatedAt})
: super(book);
@override
final String id;
// ...
}
Last modified 1yr ago