Solidity WIP part 10

## Part 10

covers interfaces

### Part 10 video link

<https://www.youtube.com/watch?v=KQ8bTt6Jhjk>

### Part 10 related .sol files

- [MyInterface.sol](./contracts/MyInterface.sol)

- [MyPayable.sol](./contracts/MyPayable.sol)

### Part 10 notes

- when looking at OpenZeppelin contracts, ERC721 inherits IERC721 which is an interface (blueprint)

- anything that implements an interface has to implement the functions defined in it

  - this is basically a list of function definitions

- interfaces can inherit from other interfaces

- in interface, all declarations of functions must be external

  - calls will come from the outside

- an interface can't have its own constructor

- you cannot declare state variables in a contract either

- if you add `payable` to an `address` type variable, that address will actually be able to receive eth

- you can make constructors and functions payable if you want to send ether to them

  - allows for extra functionality

- if a constructor is payable, you have to send the ether with the contract deployment

- 

## Part 11

### Part 11 video link

// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

contract MyPayable {

    address payable public myAddress;

    constructor() payable {

        myAddress = payable(msg.sender);

    }

    // function deposit() public payable {

        // payable(msg.sender).transfer(1); // transfers 1 eth to the contract creator

    // }

    function deposit() public payable {}

    function getThisContractBalance() public view returns (uint256) {

        uint256 amount = address(this).balance;

        return amount; 

    }

}

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