I have a mapping in my smart contract with bytes32 keys and bytes values. How can I check if bytes value exists for specific key?
Mapping is something like this:
mapping(bytes32 => bytes) public Countries;
1 Answer
You can check it via .length. It will be 0 if it is empty/uninitialised.
Countries[key].length
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2On solc v.0.6.0 this actually returns True, It sees
b'\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00'as length 32 @ivicaa– alperJan 6, 2020 at 11:39
bytes32: ``` Countries[_user] == "" // Returns true ifCountries[_user]is not initialized ``` --- pragma solidity ^0.6.0; mapping(address => bytes32) public Countries; function isCountriesInitialized(address _user) external view returns (bool) { if (Countries[_user] == "") return false; return true; } --- I observe that onsolidity v0.6.0it may return 32 for length even though it is not mapped. Example of its returned value:b'\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00'