Solidity Exercise - User Data 20210623

[NicolaBernini]

Overview

Solidity Exercise - User Data 20210623

Solidity Exercise Description

https://github.com/kevaundray/SmartContractChallenges/blob/master/Ethereum/1/Info.md

Brief Description

- Create a smart contract that stores the name and age of a given person. 
- Accounts are not allowed to change the name of other accounts name and age.

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Solution 1

Code

pragma solidity ^0.5.0; 
pragma experimental ABIEncoderV2;

contract Users{
    struct user_data{
        string name; 
        uint8 age;

    }

    struct _user_data{
        user_data data;
        bool is_present;
    }

    mapping(address => _user_data) data; 

    function set(string memory name, uint8 age) public {
        data[msg.sender].data.name = name; 
        data[msg.sender].data.age = age; 
        data[msg.sender].is_present = true; 
    }

    function get() public view returns (user_data memory) {
        require(data[msg.sender].is_present, "User not registered");
        return data[msg.sender].data; 
    }

}

Comments

Data Structures

1. struct user_data

• It contains the data to be associated to a user that is identified by its address on the Blockchain

2. struct _user_data

• A wrapper for user_data to discriminate if the user has registered before
• It uses the fact a lookup for a non existing user returns the default value of each type and for bool is_present it is false
• When a user registers, the corresponding bool is_present is set to true

3. mapping data

• The mapping associating the User address with its user_data

• This is not public since we want to access this data structure through

Functions

• Getter and Setter Functions only

1. get()

• Requires a user has registered before
• Returns the user_data associated to the address of the user, via the data mapping and using the ABIEncoderV2 feature to automatically encode the struct user_data into a tuple

2. set()
   • It encodes the passed data into a struct user_data that is associated to address of the user via the mapping data and it also sets the is_present flag

Appunto