Interface

Interfaces are similar to abstract contracts and are created using interface keyword. Following are the key characteristics of an interface.

• Interface can not have function with implementation.

• Functions of an interface can be only of type external.

• Interface can not have constructor.

• Interface can not have state variables.

• Interface can have enum, structs which can be accessed using interface name dot notation.

Example

pragma solidity ^0.5.0;

interface Calculator {
   function getResult() external view returns(uint);
}
contract Test is Calculator {
   constructor() public {}
   function getResult() external view returns(uint){
      uint a = 1; 
      uint b = 2;
      uint result = a + b;
      return result;
   }
}