strings

• strings are internally stored as bytes array

• they are then converted as UTF-8 again

• difficult to work with, and expensive.

• don't expect to work much with strings: instead use events!

• need to specify with memory keyword when passing string as parameter

// SPDX-License-Identifier: GPL-3.0
pragma solidity 0.8.1;

contract StringExample {
    string public myString = 'hello world!';

    function setMyString(string memory _myString) public {
        myString = _myString;
    }

of all the value types, string is the exception in that you are expected to declare memory when passing it as a parameter into a function.

The rest (u)int, address, boolean do not require any specification.

strings should be 32 bytes or less, otherwise they use 2 words in memory.

require(nameOwner[_name] == address(0), "The provided name has already been registered!");
require(nameOwner[_name] == address(0), "Already registered!");

• The provided name has already been registered! -> 46 characters, totalling 46 bytes.

• Already registered! -> 19 characters, totalling 19 bytes

Compact Strings

EVM stores data in 32 byte 'buckets' or 'slots'.

Strings are arrays of UTF-8 characters, and arrays are basically a fixed length sequence of storage slots located next to each other. Therefore, like everything else we need to think in terms of storage buckets

This means that when we compile our contracts, we would prefer to use a single slot for the strings we use.

Each character in a string is a UTF-8 Encoded byte, meaning that your strings can be up to 32 characters in length if you do not use specially encoded characters like emojis to be contained in a single storage slot.

Here's a great resource to look up how many bytes a string takes up under UTF-8 Encoding. https://mothereff.in/byte-counter https://blog.hubspot.com/website/what-is-utf-8

Equality comparison

https://ethereum.stackexchange.com/questions/97394/check-if-calldata-contains-string You cannot compare bytes or string using == in Solidity. You can however compare bytes32, so a simple solution is to hash the bytes first using keccak256 and compare the result of that.

For example:

function checker(bytes calldata _data) external pure returns (bool) {
  return keccak256(_data) == keccak256(abi.encodePacked("SOMETHING"));
}