[Ethereum] Function declared as pure, but this expression (potentially) reads from the environment or state and thus requires “view”

contract-debuggingsolidity

I can't work out how to modify this…When I change pure to view I get a different error:

function balanceOf(address _owner) public pure returns (uint256 balance) {
    return balances[_owner];
}

changing to view gives this error:

Overriding function changes state mutability from "pure" to "view".
    function balanceOf(address _owner) public view returns (uint256 balance) {
    ^
Spanning multiple lines.

Best Answer

You're fine. Because you're reading a state variable with Blockchain data (ie the reserved keywords like tx, msg, and so on) it's giving you a compiler warning as the compiler is not smart enough to understand that you're not actually modifying anything.

Also make sure getCoinAge is also marked view. http://solidity.readthedocs.io/en/develop/miscellaneous.html?highlight=Pure

Related Solutions

Solidity – Handling Unimplemented Functions in Contracts

The problem is that totalSupply() implementation is missing. Seems like autogenerated getters do not count. So you need to explicitly create the function.

contract StandardToken is Token {
    uint256 _totalSupply;

    function totalSupply() constant returns (uint256 totalSupply) {
        totalSupply = _totalSupply;
    }
}

Solidity View Function Error – Expression Modifies State Requires Payable

Let's go over the compilation error that you're getting:

Function declared as view

That one is clearly true, since this is how you've declared the function:

function getHighestBidID() public onlyOwner view ...

But this expression modifies the state

That one is also true, since you are indeed modifying one of the state-variables:

winneraddress = _highestidaddress;

A view function can read state-variables, but it cannot write (modify) them.

So either get rid of the view, or get rid of the winneraddress = _highestidaddress.

Best Answer

Related Solutions

Solidity – Handling Unimplemented Functions in Contracts

Solidity View Function Error – Expression Modifies State Requires Payable

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