Truffle compile SyntaxError No visibility specified Did you intend to add public

Question

When I run truffle compile I am getting this error:

/home/user/truffle/contracts/Hello-world.sol:1:1: SyntaxError: Source file requires different compiler version (current compiler is 0.5.0+commit.1d4f565a.Emscripten.clang - note that nightly builds are considered to be strictly less than the released version

pragma solidity ^0.4.15;

^----------------------^

,/home/user/truffle/contracts/Hello-world.sol:7:4: SyntaxError: No visibility specified. Did you intend to add "public"?

   function Hello_world() {

   ^ (Relevant source part starts here and spans across multiple lines).

Compilation failed. See above.

I added public keyword and tried again:

pragma solidity ^0.4.15;


contract Hello {


   string public message;


   public function Hello_world() {


   message = "Hello World!";


   }

}

No use

sudo truffle compile

Error parsing /home/user/truffle/contracts/Hello-world.sol: ParsedContract.sol:7:4: ParserError: Function, variable, struct or modifier declaration expected.

   public function Hello_world() {

   ^----^

Compilation failed. See above.

Answer 1

The solution you thought is right. The solution is to define it as public. But the way you did it is wrong. The right way to define is like this:

public function Hello_world() public {

//function body

}

Answer 2

You can try another method :

contract HelloWorld{

      function sayHello() public returns(string memory){

        return("Hello world");

      }

}

Comments

Hi. Can you explain how returning string memory will specify the visibility?