The body might complete normally, causing ‘null’ to be returned, but the return type, ‘widget’, is a potentially non-nullable type. try adding either a return or a throw statement at the end.

The ‘null’ return issue in Dart

In Dart, when a function or method has a non-nullable return type (denoted by adding a ‘?’ after the type), it is required to either have a return statement or throw an exception at the end of the function body. If the function body completes normally without a return statement, Dart will implicitly return ‘null’ for non-nullable types, leading to a compile-time error.

Let’s see an example to understand this better:

    
void myFunction() {
  // Function body
  
  // Missing return or throw statement
}

void main() {
  myFunction();
}
    
  

In the above code, the function myFunction() does not have a return or throw statement at the end. Since it has a non-nullable return type, Dart will implicitly return ‘null’ causing a compile-time error. This error can be fixed by adding either a return statement or throw statement at the end of the function body.

Here’s an updated example with a return statement:

    
String myFunction() {
  // Function body
  
  return "Hello World";
}

void main() {
  String result = myFunction();
  print(result);
}
    
  

In the updated code, the function myFunction() now has a return statement at the end. It returns a string “Hello World”. In the main() function, the returned value is stored in the variable result and printed to the console.