How to add variable into the string in solidity?

Question

I want to add the extractedStr variable into the path?

bytes memory extractedStr;
string memory combine = '<path d="string(extractedStr)" fill="#FFFFFF"/>';

Answer 1

Your problem is basically a string concatenation problem.

Since Solidity v0.8.12, you concatenate strings easily using:

string.concat(s1, s2)

You can check solidity docs on strings and bytes for documentation reference.

In your case, this should help you concatenate your strings:

string public s1 = "string(";
string public s2 = ")";
bytes public yourBytes = '0x100';
string public combined;

function combine() public {
    combined = string.concat(s1, string(extractedStr), s2);
}

The combined string variable will now return:

'string(0x100)'

Answer 2

version 0.8.12 or higher

    function concatA() external pure returns (string memory) {
        bytes memory extractedStr = '0xFFFF00';
        return string.concat('<path d="', string(extractedStr) ,'" fill="#FFFFFF"/>');
    }

result 0:string: <path d="0xFFFF00" fill="#FFFFFF"/>

otherwise for earlier versions

    function concatB() external pure returns (string memory) {
        bytes memory extractedStr = '0xFFFF00';
        return string(abi.encodePacked('<path d="', string(extractedStr) ,'" fill="#FFFFFF"/>'));
    }

result 0: string: <path d="0xFFFF00" fill="#FFFFFF"/>