Mappings.sol

pragma solidity ^0.6.0;

contract MyContract {
    // Mappings
    mapping(uint => string) public names;
    mapping(uint => Book) public books;
    mapping(address => mapping(uint => Book)) public myBooks;

    struct Book {
        string title;
        string author;
    }

    constructor() public {
        names[1] = "Adam";
        names[2] = "Bruce";
        names[3] = "Carl";
    }

    function addBook(uint _id, string memory _title, string memory _author) public {
        books[_id] = Book(_title, _author);
    }
    
    function addMyBook(uint _id, string memory _title, string memory _author) public {
        myBooks[msg.sender][_id] = Book(_title, _author);
    }
}

This is very cool. So what if I want to get all books under a particular sender? like a getSendersBooks function? How will that look like? Thank you.

@gwmccubbin

Hi Greg, Why am I facing such error when I add book. It shows this error. What I need to do about it?

transact to MyContract.addBook errored: Error encoding arguments: Error: invalid BigNumber string (argument="value", value="MyBook", code=INVALID_ARGUMENT, version=bignumber/5.5.0)

Hi Greg, Why am I facing such error when I add book. It shows this error. What I need to do about it?

transact to MyContract.addBook errored: Error encoding arguments: Error: invalid BigNumber string (argument="value", value="MyBook", code=INVALID_ARGUMENT, version=bignumber/5.5.0)

Change the first line version code with "pragma solidity >=0.4.16 <0.9.0;" .. It should work

Found this very helpful. Thank you!