Typedef Keyword :

• In Dart, the typedef is used to generate an alias for function type that we can use it as type annotation for declaring variables and return types of that function type. An alias of function type can be used as type annotation in variable declaration or function return type. A typedef stores the type information when we assigned the function type to a variable.

Declaring a typedef :

• A typedef keyword is used to create an alias for function that will be the same as the actual functions. We can also create a function prototype with a list of parameters. The syntax is given below.

syntax :

•   typedef function_name(parameters)
  

Example :

• Let's create an alias of MultiOperation(int n1, int n2) that contains two parameters of the integer type.

•   typedef MultiOperation(int n1, int n2);   // function signature
  

Assigning typedef Variable :

• We can assign any function with the same parameter to the typedef variable. The syntax is given below.

Syntax :

•   type_def var_name = function_name;
  

typedef realexam(int one, int two);
real1(int one, int two) {
  print('object called with a');
  print('object called with b $one and $two');
}

real2(int one, int two) {
  print('object called without a');
  print('$one + $two');
}

void main() {
  realexam obj = real1;
  obj(1, 2);
  obj = real2;
  obj(3, 4);
  print(obj);
}

• Output :

object called with a
object called with b 1 and 2
object called without a
3 + 4
Closure: (int, int) => dynamic from Function 'real2': static.

Exited.