Freezed class

A data-class macro.

Warning: Macros are still an experimental feature of Dart. Lots of features are missing, so expect bugs.

This macro generates a toString, copyWith, ==, and hashCode implementation for a class.

Note: copyWith supper class.copyWith(field: null). This will clone the object with fieldset tonull`.

hashCode, == and toString won't be generated if the class already possesses an implementation of those methods.

Two possible syntaxes are supported:

  • Constructor-first. You define a class with a constructor, and the macro will generate fields for you. This gives fine-grained control over positional vs named parameters. It offers the ability to use asserts, super, ... Although macros have still lots of things related to this that don't work. So although the syntax is very flexible, lots of things are not supported yet.

  • Field-first. You define a class with fields, and the macro will generate a constructor for you. This is the most stable syntax. But it is less flexible, and not very dart-like. If you want full control over constructors, you'll have to use the constructor-first syntax.

Constructor-first usage

To use the constructor-first syntax, define a class with a constructor, but no fields:

@Freezed()
class Example {
  Example({required int foo, required String bar});
}

The macro will generate the fields for you, along with the various methods.

void main() {
  final example = Example(foo: 42, bar: '42');
  print(example.foo); // 42
}

Using named constructors.

Naturally, the macro expects that you use the default constructor. If you wish to generate fields based on a named constructor instead, specify @Freezed(constructor: '<constructor name>').

@Freezed(constructor: 'custom')
class Example {
 Example.custom({required int foo, required String bar});
}

Field-first usage

To use the field-first syntax, define a class with fields but default constructor. The macro will then generate a constructor for you, along with the various methods.

@Freezed()
class Example {
 final int foo;
 final String bar;
}

Currently, all fields are "named" parameters, and they are optional if they are nullable.

void main() {
 final example = Example(foo: 42, bar: '42');
 print(example.foo); // 42
}

Specifying the constructor name

If you wish to generate a non-default constructor, you can specify @Freezed(constructor: '<constructor name>').

@Freezed(constructor: 'custom')
class Example {
  final int foo;
}

void main() {
  final example = Example.custom(foo: 42);
}

Constructors

Freezed({String? constructor, bool makeCollectionsUnmodifiable = true, String? superCtor})
const

Properties

constructor → String?
The name of the constructor to use.
final
hashCode → int
The hash code for this object.
no setterinherited
makeCollectionsUnmodifiable → bool
final
runtimeType → Type
A representation of the runtime type of the object.
no setterinherited
superCtor → String?
The name of the super constructor to call.
final

Methods

buildDeclarationsForClass(ClassDeclaration clazz, MemberDeclarationBuilder builder) → FutureOr<void>
noSuchMethod(Invocation invocation) → dynamic
Invoked when a nonexistent method or property is accessed.
inherited
toString() → String
A string representation of this object.
inherited

Operators

operator ==(Object other) → bool
The equality operator.
inherited