Flutter/Dart - Difference between () {} and () => {}

Question

In Flutter/Dart the examples sometimes show fat arrow and sometimes dont. Here are examples:

RaisedButton(
  onPressed: () {
    setState(() {
      _myTxt = \"         


        

Answer 1

=> is used to return a value of an anonymous function.

() {} lets you execute multiple statements.

while

() => {myVar} or () => myVar; allows one single statement.

() => myVar; is short and simple when returning one statement.

The same logic goes for creating non anonymous functions too.

Single statement func func() => y = x + x;

Multiple statement func

func () {
   x = x + x; 
   print(x + ' value of x');
};