Callable classes in Dart

In this article, we are going to learn about the Callable classes in Dart.

Callable class?

Dart facilitates us to call the class instances like a function.

To allow an instance of your Dart class to be called like a function, implement the call() method from the Dart official. Please check the below code:

class ClassAsFunction {
  int call(int a, int b) => a * b;
}

var callableClass = ClassAsFunction();
var res = callableClass(4,4);

void main() => print(res);

class ClassAsFunction {

int call(int a, int b) => a * b;

}

var callableClass = ClassAsFunction();

var res = callableClass(4,4);

void main() => print(res);

Output: 16

In the above example, the ClassAsFunction class defines a call() function that takes two integers and returns the product of them.

Note: Dart doesn’t allow us to create multiple call() functions for a class and if you do that, Dart raises the compilation error. Please check the below code:

class ClassWithMultipleCall {
  int call(int a, int b) => a * b;
  int call(int a, int b, int c) => a * b * c;
}

var callableClass = ClassWithMultipleCall();
var res = callableClass(4,4);

void main() => print(res);

class ClassWithMultipleCall {

int call(int a, int b) => a * b;

int call(int a, int b, int c) => a * b * c;

}

var callableClass = ClassWithMultipleCall();

var res = callableClass(4,4);

void main() => print(res);

error The name ‘call’ is already defined.

Thanks for reading.

Happy Coding 🙂

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Ravi Kishor 30 June 2022

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Callable classes in Dart

Callable class?

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