Parameters

DO

DO use = to separate a named parameter from its default value.

For legacy reasons, Dart allows both : and = as the default value separator for named parameters. For consistency with optional positional parameters, use =.

void insert(Object item, {int at = 0}) { ... }

void insert(Object item, {int at: 0}) { ... }

DON'T

DON’T use an explicit default value of null.

If you make a parameter optional but don’t give it a default value, the language implicitly uses null as the default, so there’s no need to write it.

void error([String message]) {
  stderr.write(message ?? '\n');
}

void error([String message = null]) {
  stderr.write(message ?? '\n');
}