如何在 FLUTTER 中的 RaisedButton.onpressed 中传递对 function 的引用，但带有参数？

Question

I already understood that we should call functions in FLUTTER without parentheses because you want to establish a reference to that function, not execute it.

But what if you want to pass parameters to that function? How can I tell FLUTTER that I want to reference the function (not execute it), but pass arguments to it? The arguments are usually specified inside parentheses.

I tried calling a function with parentheses when I have parameters to indicate, and it seems to work perfectly. It only executes the function when the button is pressed.... I'm a little confused.

Answer 1

If the parameters line up you can pass a reference to the function and it will be called with those parameters.

String validate(String? value) {
  if (value == null) {
    return 'Required';
  }
  return null;
}

TextFormField(
  // Signature of validator and validate are the same
  validator: validate
)

If the signatures don't overlap you have to use an anonymous function.

TextFormField(
  validator: (value) => someOtherFunction(),
)