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I'm attempting to write a contract which a variety of classes can inherit that give the inherited class access to various state variables of the child when called by name.

I.e. if parent has a function "food()" which returns 'hamburger', the inherited function is able to access the value of food by calling getAttribute("food()");

I tried to do it like this, but the success variable returns false consistently.

The child contract is as follows inherits from a contract called reader.

pragma solidity >=0.7.0 <0.9.0;
import "./reader.sol";

contract mymain is reader {
    constructor() {
       myAddress=address(this);
    }
    function getName() public pure returns(string memory) {
        return "foo";
    }
    function getFood() public pure returns(string memory) {
        return "hamburger";
    }
}

contract reader { 
    address myAddress;
    function getAttribute(string memory functionName) public view returns(string memory) {
        bytes memory payload = abi.encodePacked(functionName); 
        bool success;
        bytes memory b;
        (success, b)=myAddress.staticcall(payload);
        if (!success) return "failed";
        return(string(b));
    }
}

When I deploy mymain and call mymain.getAttribute("getFood()"); I expect it to return hamburger but it returns failed. I am unfamiliar with the right way to encode the function selector, but obviously doing something wrong.

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  • I was able to get this work (sort of) by changing abi.encodePacked to abi.encodeWithSignature but I"m not sure why. the bytes array when converted back to a string was padded at the beginning and end with a garbage characters (mostly codePoint 0, but one or two random other unrpintables like 17). If anybody knows why that is it would be helpful.
    – GGizmos
    Apr 7, 2022 at 5:03

1 Answer 1

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It should be:

bytes memory payload = abi.encodeWithSignature(functionName); 

Instead of:

bytes memory payload = abi.encodePacked(functionName); 

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