Dart has two types of optional parameters: named and positional
A parameter wrapped by [ ] is a positional optional parameter.
A parameter wrapped by { } is a names optional parameter.
Example with positional optional parameter:
function1 (String name, [int age = 31]) {
}
Calling function1:
- function1('Smith');
- function1('Smith', 48);
Example with names optional parameter:
function2(String name, {int age = 31}) {
}
Calling function2:
- function2('Lars');
- function2('Lars', alder: 48);
Note: You may use positional optional parameters or named optional parameters,
but not both in the same function or method.