Conversion of uint to string

Question

I am trying to convert uint to string in solidity. Is it possible to convert? if so how can I convert it?

Convertion to base 10 is prefered, but in hexadecimal might also be helpful.

Answer 1

Another option is to use a solution from Oraclize https://github.com/oraclize/ethereum-api/blob/master/oraclizeAPI_0.5.sol, it suits best for me:

0.5 Compiler Version:

    function uint2str(uint _i) internal pure returns (string memory _uintAsString) {
    if (_i == 0) {
        return "0";
    }
    uint j = _i;
    uint len;
    while (j != 0) {
        len++;
        j /= 10;
    }
    bytes memory bstr = new bytes(len);
    uint k = len - 1;
    while (_i != 0) {
        bstr[k--] = byte(uint8(48 + _i % 10));
        _i /= 10;
    }
    return string(bstr);
}

Pre 0.5 Compiler Version:

function uint2str(uint i) internal pure returns (string){
    if (i == 0) return "0";
    uint j = i;
    uint length;
    while (j != 0){
        length++;
        j /= 10;
    }
    bytes memory bstr = new bytes(length);
    uint k = length - 1;
    while (i != 0){
        bstr[k--] = byte(48 + i % 10);
        i /= 10;
    }
    return string(bstr);
}

Answer 2

You can convert the uint to bytes32 by using bytes32 data = bytes32(u) (uint is same uint256 How to convert a uint256 type integer into a bytes32?)

Then use How to convert a bytes32 to string:

function bytes32ToString (bytes32 data) returns (string) {
    bytes memory bytesString = new bytes(32);
    for (uint j=0; j<32; j++) {
        byte char = byte(bytes32(uint(data) * 2 ** (8 * j)));
        if (char != 0) {
            bytesString[j] = char;
        }
    }
    return string(bytesString);
}

Answer 3

Solidity is character set agnostic concerning strings. There is no built-in "toString" in Solidity. https://github.com/pipermerriam/ethereum-string-utils is a library that can help:

> stringUtils.uintToBytes(1234)
"1234"

The MIT licensed implementation is:

function uintToBytes(uint v) constant returns (bytes32 ret) {
    if (v == 0) {
        ret = '0';
    }
    else {
        while (v > 0) {
            ret = bytes32(uint(ret) / (2 ** 8));
            ret |= bytes32(((v % 10) + 48) * 2 ** (8 * 31));
            v /= 10;
        }
    }
    return ret;
}

Answer 4

Dmitriy Vinokurov answer does not work in solidity 0.8.0. This is a revised version:

 function uint2str(
  uint256 _i
)
  internal
  pure
  returns (string memory str)
{
  if (_i == 0)
  {
    return "0";
  }
  uint256 j = _i;
  uint256 length;
  while (j != 0)
  {
    length++;
    j /= 10;
  }
  bytes memory bstr = new bytes(length);
  uint256 k = length;
  j = _i;
  while (j != 0)
  {
    bstr[--k] = bytes1(uint8(48 + j % 10));
    j /= 10;
  }
  str = string(bstr);
}

Answer 5

Based on the Oraclize code that Dmitry supplied I made a function to return a uint as a string in hex format:

function uint2hexstr(uint i) internal pure returns (string) {
    if (i == 0) return "0";
    uint j = i;
    uint length;
    while (j != 0) {
        length++;
        j = j >> 4;
    }
    uint mask = 15;
    bytes memory bstr = new bytes(length);
    uint k = length - 1;
    uint numStart = 48;
    uint letterStarn = 65;
    while (i != 0){
        uint curr = (i & mask);
        bstr[k--] = curr > 9 ? byte(55 + curr ) : byte(48 + curr); // 55 = 65 - 10
        i = i >> 4;
    }
    return string(bstr);
}

https://gist.github.com/okwme/f3a35193dc4eb9d1d0db65ccf3eb4034