Visibility

Functions and state variables have to declare whether they are accessible by other contracts.

Functions can be declared as

• public - any contract and account can call
• private - only inside the contract that defines the function
• internal - only inside contract that inherits an internal function
• external - only other contracts and accounts can call

State variables can be declared as public, private, or internal but not external.

Private

Private function can only be called

• inside this contract
• Contracts that inherit this contract cannot call this function.

   function privateFunc() private pure returns (string memory) {
       return "private function called";
   }

   function testPrivateFunc() public pure returns (string memory) {
       return privateFunc();
   }

Internal

Internal function can be called

• inside this contract
• inside contracts that inherit this contract

    function internalFunc() internal pure returns (string memory) {
        return "internal function called";
    }

    function testInternalFunc() public pure virtual returns (string memory) {
        return internalFunc();
    }

Public

Public functions can be called

• inside this contract
• inside contracts that inherit this contract
• by other contracts and accounts

    function publicFunc() public pure returns (string memory) {
        return "public function called";
    }

External

External functions can only be called

• by other contracts and accounts

    function externalFunc() external pure returns (string memory) {
        return "external function called";
    }

Example