Optional Named Parameter

Unlike positional parameters, the parameters name must be specified while the value is being passed. Curly brace {} can be used to specify optional named parameters.

Syntax - Declaring the function

 void function_name(a, {optional_param1, optional_param2}) { } 

Syntax - Calling the function

 function_name(optional_param:value,); 

Example

 void main() { test_param(123); test_param(123,s1:'hello'); test_param(123,s2:'hello',s1:'world'); } test_param(n1,{s1,s2}) { print(n1); print(s1); } 

It should produce the following output−

 123 null 123 hello 123 world