Anonymous Functions

In the previous lesson we introduced you to functions that are defined by using a function name like main(), fullName(). In this lesson we will talk about nameless functions or functions without a name. This type of function is known as an anonymous function, lambda, or closure. An anonymous function behaves the same as a regular function, but it does not have a name with it. It can have zero or any number of arguments / parameters with an option type annotation.

Syntax 

Below is the syntax of the anonymous function

(parameters){
  // body of an anonymous function
}

Knowledge Panel:

• You can assign an anonymous function to a variable
• You can pass an anonymous function as a parameter / argument

Example 1:

In this example, you will learn to use an anonymous function to print all list items. This function invokes each fruit without having a function name.

void main() {
  // List of fruits
  var fruits = ['Apple', 'Banana', 'Cherry', 'Date'];

  // Using an anonymous function with forEach to print each fruit
  fruits.forEach((fruit) {
    print(fruit);
  });
}

Explanation:

• var fruits = [‘Apple’, ‘Banana’, ‘Cherry’, ‘Date’];: Defines a list of fruits.
• fruits.forEach((fruit) { … });: The forEach method is used to iterate over each item in the list. It takes an anonymous function as its argument.
  • (fruit) { print(fruit); }: This is an anonymous function (a function without a name) that takes one parameter fruit and prints it.

Example 2:

In this example, we will use an anonymous function to print all list items.

void main() {
  // List of items
  var items = ['Laptop', 'Tablet', 'Smartphone', 'Smartwatch'];

  // Using an anonymous function with forEach to print each item
  items.forEach((item) {
    print(item);
  });
}

Explanation:

• var items = [‘Laptop’, ‘Tablet’, ‘Smartphone’, ‘Smartwatch’];: Defines a list of items.
• items.forEach((item) { … });: The forEach method iterates over each element in the list and applies the provided anonymous function.
  • (item) { print(item); }: This is an anonymous function that takes one parameter item and prints it.