Constructors Design

Domains: Dart

CONSIDER

CONSIDER making your constructor const if the class supports it.

If you have a class where all the fields are final, and the constructor does nothing but initialize them, you can make that constructor const. That lets users create instances of your class in places where constants are required—inside other larger constants, switch cases, default parameter values, etc.

If you don’t explicitly make it const, they aren’t able to do that.

Note, however, that a const constructor is a commitment in your public API. If you later change the constructor to non-const, it will break users that are calling it in constant expressions. If you don’t want to commit to that, don’t make it const. In practice, const constructors are most useful for simple, immutable data record sorts of classes.

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Constructor

You can create an object using a constructor. Constructor names can be either ClassName or ClassName.identifier. Code creates Point objects using the Point() and Point.fromJson() constructors. The new keyword became optional in Dart 2. Some classes provide constant constructors. To create a compile-time constant using a constant constructor, put the const keyword before the constructor name.

Default parameter values

Your function can use = to define default values for both named and positional parameters. The default values must be compile-time constants. If no default value is provided, the default value is null. How to set default values for positional parameters. You can also pass lists or maps as default values.

Classes

Dart is an object-oriented language with classes and mixin-based inheritance. Every object is an instance of a class, and all classes descend from Object. Mixin-based inheritance means that although every class (except for Object) has exactly one superclass, a class body can be reused in multiple class hierarchies.