dart advantage of a factory constructor identifier

Question

I\'ve been investigating JSON parsing for my Flutter app and have a question about factory constructors that I can\'t resolve. I\'m trying to understand the advantage of usi

Answer 1

A factory constructor vs. a normal constructor

• A factory constructor invokes another constructor.
• Since a factory constructor does not directly create a new instance, it cannot use a constructor initializer list.
• A normal constructor always returns a new instance of the class. A factory constructor is permitted to return an existing instance, an instance of a derived class, or null. (However, some people dislike returning null from a factory constructor.)

A factory constructor vs. a static method

• A factory constructor can be the unnamed, default constructor of a class.
• A factory constructor can be used with new. (But using new is now discouraged.)
• Static methods can be used to create tear-offs (i.e., they can be used as callbacks) but constructors currently can't.
• Static methods can be async. (A factory constructor must return a type of its class, so it cannot return a Future.)
• Factory constructors can be declared const.
• In generated dartdoc documentation, a factory constructor obviously will be listed in the "Constructors" section (which is prominently at the top) whereas a static method will be in the "Static Methods" section (which currently is buried at the bottom).