What is the difference between named and positional optional parameters in Dart?

Short answer

Named parameters are passed by name and make the intent clear, while positional optional parameters depend on their order and can have a default value.

Explanation

Use named parameters when readability and distinction matter more, especially with more than one optional option. A named parameter can be made required with required, and a default value can be given to an optional positional or named parameter. A good signature design reduces passing values in an order that is hard to review.

Code example

void greet(String name, {String punctuation = "!"}) {
  print("Hello $name$punctuation");
}

greet("Dart", punctuation: ".");

Common mistakes

• Treating every named parameter as optional; required changes that.
• Overusing positional parameters, making the function call unclear.

Follow-up questions

• How does the null safety system work in Dart?

Sources

• Dart language — Functions