flutter - Why we have to put state changing logic inside the call back of setState?

Question

Whether we put state changing logic inside the call back of setState or not, the result is the same. The following code snippets behave the same.

class _MyWidgetState extends State<MyWidget> {
  int _counter = 0;
  
  void _incrementCounter() {
    _counter++;
    setState((){});
  }
}


class _MyWidgetState extends State<MyWidget> {
  int _counter = 0;
  
  void _incrementCounter() {
    setState((){
      _counter++;
    });
  }
}

question from:https://stackoverflow.com/questions/65845693/why-we-have-to-put-state-changing-logic-inside-the-call-back-of-setstate

Answer 1

You should do all your mutations inside the closure, and the computing outside of the closure.

It's doesn't explicitly say that anything about if it's different to call is in or outside the function. But it does recommend putting it inside. From my point of view, it's more clear and readable if you put the changes inside the setState function

Calling setState notifies the framework that the internal state of this object has changed in a way that might impact the user interface in this subtree, which causes the framework to schedule a build for this State object.

You can see more at official Doc