Solidity 044 Interface
// SPDX-License-Identifier: MIT
pragma solidity ^0.8.9;
// Define an interface IHelloWorld. Interfaces are used to define contracts' external functions without implementing them.
interface IHelloWorld {
// Declare an external function GetValue that, when implemented, will return a uint value.
function GetValue() external view returns (uint);
// Declare an external function SetValue that takes a uint _value as input.
function SetValue(uint _value) external;
}
// Implement the IHelloWorld interface with a contract named HelloWorld.
contract HelloWorld is IHelloWorld {
// Declare a private uint variable to store a simple integer value.
uint private simpleInteger;
// Implement the GetValue function defined in the IHelloWorld interface.
// This external view function returns the current value of simpleInteger.
function GetValue() external view override returns (uint) {
return simpleInteger;
}
// Implement the SetValue function defined in the IHelloWorld interface.
// This external function updates the value of simpleInteger.
function SetValue(uint _value) external override {
simpleInteger = _value;
}
}
// Define a contract named Client to demonstrate interaction with the HelloWorld contract via the IHelloWorld interface.
contract Client {
// Define a public function that demonstrates setting and getting a value from the HelloWorld contract.
function GetSetIntegerValue() public returns (uint) {
// Instantiate a new HelloWorld contract and assign it to the interface type IHelloWorld.
IHelloWorld myObj = new HelloWorld();
// Set the value of simpleInteger in the HelloWorld contract to 100.
myObj.SetValue(100);
// Get the current value of simpleInteger from the HelloWorld contract, add 10 to it, and return the result.
// Note: The original approach will work, but typically you'd interact with the contract directly
// if it's being created within the same transaction for efficiency.
return myObj.GetValue() + 10;
}
}
