Solidity Warning

Question

I want to know what's wrong with my function, 'cause Visual Studio Code give me warning :

function state mutability can be restricted to view

this is my function :

  function verifyVote(address pers) public returns (uint){

    for (uint i = 0; i < personne.length; i++){
        if (pers == personne[i].own) {
            if (personne[i].isVoted == true){
                return 1;
            }
            else{
                return 0;
            }
        }
    }

    return 404;
} 

Answer 1

Your function doesn't modify the state, so it can be declared as a view function.

From the documentation:

Functions can be declared view in which case they promise not to modify the state.

function verifyVote(address pers) public view returns (uint){
    for (uint i = 0; i < personne.length; i++){
        if (pers == personne[i].own) {
            if (personne[i].isVoted == true){
                return 1;
            }
            else{
                return 0;
            }
        }
    }
    return 404;
}

Answer 2

Your contract contains a state variable personne[].

Your function verifyVote() only reads values from your contract storage, by looping through each elements of the personne[] array. It does not modify the values.

From the Solidity documentation

Functions can be declared view in which case they promise not to modify the state.

• view = read, write
• pure = read, write
• No specifier = read, write

So the view specifier ensures that your function is restricted to read-only.