Introduction

In Dart, functions are objects too. It is an object of type Function. Similar to other objects, functions can be passed as arguments to other functions and can be assigned to variables as well.

A callable class allows its instance to be called as a function. This feature of the Dart language is useful for making named-functions.

Implementing a callable Class

All Dart functions have a call method. To make a class Callable, the call() method needs to be implemented. Let’s declare a callable class below:

class Addition {
  int call(int a, int b) => a + b;
}

The above class’ call method takes two arguments and returns their sum.

Using a callable Class

Let’s check out using the Addition callable class in the code below. The addition object is of the Addition type. Now, addition(1, 2) can be called to calculate the sum of the given numbers.