Solidity

Interfaces are the same as abstract contracts created by using an interface keyword, also known as a pure abstract contract. Interfaces do not have any definition or any state variables, constructors, or any function with implementation, they only contain function declarations i.e. functions in interfaces do not have any statements. Functions of Interface can be only of type external. They can inherit from other interfaces, but they can’t inherit from other contracts. An interface can have enum, structs which can be accessed using interface name dot notation.

Example: In the below example, the contract thisContract implements an interface InterfaceExample and implements all the interface functions.

// Solidity program to  
// demonstrate the working  
// of the interface 
  
pragma solidity 0.4.19; 
  
// A simple interface 
interface InterfaceExample{ 
  
    // Functions having only  
    // declaration not definition 
    function getStr( 
    ) public view returns(string memory); 
    function setValue( 
      uint _num1, uint _num2) public; 
    function add( 
    ) public view returns(uint); 
} 
  
// Contract that implements interface 
contract thisContract is InterfaceExample{ 
  
    // Private variables 
    uint private num1; 
    uint private num2; 
  
    // Function definitions of functions  
    // declared inside an interface 
    function getStr( 
    ) public view returns(string memory){ 
        return "GeeksForGeeks"; 
    } 
      
     // Function to set the values  
    // of the private variables 
    function setValue( 
      uint _num1, uint _num2) public{ 
        num1 = _num1; 
        num2 = _num2; 
    } 
      
    // Function to add 2 numbers  
    function add( 
    ) public view returns(uint){ 
        return num1 + num2; 
    } 
      
} 
  
contract call{ 
      
    //Creating an object 
    InterfaceExample obj; 
  
    function call() public{ 
        obj = new thisContract(); 
    } 
      
    // Function to print string  
    // value and the sum value 
    function getValue( 
    ) public returns(uint){ 
        obj.getStr; 
        obj.setValue(10, 16); 
        return obj.add(); 
    } 
} 

Output :

Interface Example

My Personal Notes

Solidity – Basics of Interface

Solidity

Recommended Posts: