Smart Contract: Model Divided Version with Different Associations

Solidity is an object-oriented, high-level language for implementing smart contracts. Smart contracts are programs which govern the behaviour of accounts within the Ethereum state.

Below is a different version of the smart contracts for our project, it is written with solidity v0.6.7.
With models of User, Charity, Project and Donation.

And associations between model as:

• Project belongs to one Charity
• Charity has many Project
• Project has many Donation
• Donation belongs to one Project

Users Contract:

pragma solidity >=0.4.21 <0.7.0;

contract Users {
  // using metamask login
  struct User { 
    string email;
    string name;
  }

  mapping(address => User) public users;

  //msg.sender: the person who currently connecting with the contract/ the account currently connecting with
  function createUser(string memory email, string memory name) public {
    address user = msg.sender;
    require(
      !users[user], 
      'User is already exist'
    );

    users[user] = User(email, name);
  }
}

Charities:

pragma solidity >=0.4.21 <0.7.0;

contract Charities {

  struct Charity {
    string name;
    string pictureUrl;
    string description;
  }

  mapping(address => Charity) public charities;

  function createOrg(string memory organization, string memory info) public {
    require(
      !charities[msg.sender],
      'Charity is already exist'
    );

    charities[msg.sender] = Charity(organization, info);
  }
}

Project:

pragma solidity >=0.4.21 <0.7.0;


contract Projects {
 struct Project {
    string name;
    string info;
    uint donatedAmount; // reached amount
    uint goal; // target amount
    address payable charity;
    Donation[] donations; // project has many donations
  }

  struct Donation {
    address payable user;
    uint amount;
    bool isTransfered;
  }

  Project[] public projects; // charity has many projects

  function createPro(string memory name, string memory info, uint donatedAmount, uint memory goal) public {

    projects.push(Project({
      name: name,
      info: info,
      donatedAmount: 0,
      goal: goal,
      chairty: msg.sender, // owner's wallet id..
      donations: []
      // address: address payable charity
    }));
  }


  function donate(uint memory projectId, uint memory amount) public payable {
    require(projectId < projects.length, 'Project does not exist');

    projects[projectId].donations.push(Donation({
      user: msg.sender, // donor's wallet id..
      amount: amount,
      isTransfered: false
    }));

  }
}


/*
going futher:
  - verify if receiver/owner is correct before receiving transactions
  - refund if expire
*/

Sources to look up:
solidity documentation: https://solidity.readthedocs.io/en/v0.6.7/