value_t2_generator 1.0.26

Provides a short syntax, value type (ish) way of creating classes - copywith, toString, equality

value_t2

Reasoning:

specifying clases with copywith, equals, toString, required constructor fields and other standard features is actually a fair amount of work resulting in verbose code which makes it difficult to maintain and difficult to read. typeclasses (ish), value types (ish)

Solution: use value_t2

Basic features

• Equality

var bob1 = Person(age: 5, name: "bob");
var bob2 = Person(age: 5, name: "bob");

bob1 == bob2; //true

• CopyWith (works on subclasses in same file)

var bob = Employee(age: 5, name: "bob", id: "123);
var bobby = bob.cwPerson(age: 6, name: "bobby");
var robert = bob.cwEmployee(age: 25, name: "robert", id: "123);

bobby is Employee; //true
robert is Employee; //true

• ToString

var bob = Person(age: 5, name: "bob");
bob.toString() //age:5|name:"bob"

• All fields are required, non nullable (through assert pattern) and final by default

var bob = Person(age: 5, name: "bob");
bob.age = 6; //error

//warning on missing parameter values
var bob = Person(age: 5);

//assert error if parameter is null
var bob = Person(age: 5, name: null);

More examples

For more examples look at the Examples project in the github repository

Installation

• Import value_t2_annotation, value_t2_generator, quiver_hashcode and build_runner

dependencies:
  value_t2_annotation:
  quiver_hashcode:

dev_dependencies:
  build_runner:
  value_t2_generator

Usage

• Add three imports at top of each file

import 'package:meta/meta.dart';
import 'package:quiver_hashcode/hashcode.dart';
import 'package:value_t2_annotation/value_t2_annotation.dart';

• Place a @ValueT2() annotation on every class
• Prepend a dollar on the classname or two dollars for abstract classes when defining a class
• Declare all classes as abstract

abstract class $$MyAbstract class {

abstract class $MyClass class {

• when using the class don't use the dollar sign

 MyClass(a: "value")

• simple definition

@ValueT2()
abstract class $Pet {
 String get type;
}

• simple definition with implements

 @ValueT2()
 abstract class $Person {
   String get name;
 }

 @ValueT2()
 abstract class $Employe implements $Person {
   String get id;
 }

• never use extends, only interfaces

@ValueT2()
abstract class $B implements $A {

More features

• Shorter and more simple syntax

@ValueT2()
abstract class $A {
  String get aValue;
}

//vs

class A {
  final String aValue;

  A({
    @required this.aValue,
  }) : assert(aValue != null);

  //toString, hasCode, ==
}

• The properties of interfaces are implemented automatically (no need to specify them, just use implements)

@ValueT2()
abstract class $A {
  String get aValue;
}

@ValueT2()
abstract class $B implements $A {
  String get bValue;
}

var b = B(aValue: "A", bValue: "B");

• Can override a property of a subclass

@ValueT2()
abstract class $A {
  Person get a;
}

@ValueT2()
abstract class $B implements $A {
  Employee get a;
}

• Can specify generics

@ValueT2()
abstract class $$A<T1, T2> {
  T1 get x;
  T2 get y;
}

@ValueT2()
abstract class $B implements $$A<int, String> {
  String get z;
}

Limitations

• Custom getters are not supported
  • use functions instead
• Methods on a class are not supported (use functions instead)
• 'go to definition' takes you to the generated class
  • workaround1 - to get class info hover over the class
  • workaround2 - go to definition, then go to definition a second time to go to the dollar version of class
  • possible update in the future

Coming (if others want and are interested)

See github issues