public/subjects/mobile-dev/optional-sum/README.md

Optional Sum

Instructions

Write a function named optionalSum that accepts two int arguments, and an optional int argument. Return the sum of all the arguments.

Optional parameters

In Dart, you can make function arguments optional, meaning that a function can work even if the optional argument is omitted. If the optional parameter is omitted, it is considered to be null.

A function with optional parameters:

void someFunction(int first, int second, [int? third]) {
	if (third != null) {
		print('${first}, ${second}, ${third}');
	} else {
		print('${first}, ${second}');
	}
}

void main() {
	someFunction(1, 2);
	someFunction(1, 2, 3);
}

Optional parameters must come after the required parameters.

You cannot use both optional and named parameters.