Typedef in Dart is used to create a user-defined function (alias) for other application functions,

Syntax: typedef function_name (parameters);

With the help of a typedef, we can also assign a variable to a function.

Syntax:typedef variable_name = function_name;

After assigning the variable, if we have to invoke it then we go as:

Syntax: variable_name(parameters);

Example:

// Defining alias name
typedef MainFunction(int a, int b);

functionOne(int a, int b) {
  print("This is FunctionOne");
  print("$a and $b are lucky numbers !!");
}

functionTwo(int a, int b) {
  print("This is FunctionTwo");
  print("$a + $b is equal to ${a + b}.");
}

// Main Function
void main() {
  // use alias
  MainFunction number = functionOne;

  number(1, 2);

  number = functionTwo;
 // Calling number
  number(3, 4);
}

Output:

This is FunctionOne
1 and 2 are lucky numbers !!
This is FunctionTwo
3 + 4 is equal to 7