Notes

• You can define your own type by creating a struct.
• They are useful for grouping together related data.
• Structs can be declared outside of a contract and imported in another contract.

Code

solidity
Structs.sol
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// SPDX-License-Identifier: MIT
pragma solidity ^0.8.20;

contract Todos {
   struct Todo {
       string text;
       bool completed;
   }

   // An array of 'Todo' structs
   Todo[] public todos;

   function create(string calldata _text) public {
       // 3 ways to initialize a struct
       // - calling it like a function
       todos.push(Todo(_text, false));

       // key value mapping
       todos.push(Todo({text: _text, completed: false}));

       // initialize an empty struct and then update it
       Todo memory todo;
       todo.text = _text;
       // todo.completed initialized to false

       todos.push(todo);
   }

   // Solidity automatically created a getter for 'todos' so
   // you don't actually need this function.
   function get(uint _index) public view returns (string memory text, bool completed) {
       Todo storage todo = todos[_index];
       return (todo.text, todo.completed);
   }

   // update text
   function updateText(uint _index, string calldata _text) public {
       Todo storage todo = todos[_index];
       todo.text = _text;
   }

   // update completed
   function toggleCompleted(uint _index) public {
       Todo storage todo = todos[_index];
       todo.completed = !todo.completed;
   }
}

Declaring and importing Struct

File that the struct is declared in:

solidity
StructDeclaration.sol
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// SPDX-License-Identifier: MIT
pragma solidity ^0.8.20;
// This is saved 'StructDeclaration.sol'

struct Todo {
   string text;
   bool completed;
}

File that imports the struct above:

solidity
StructImport.sol
Copy
// SPDX-License-Identifier: MIT
pragma solidity ^0.8.20;

import "./StructDeclaration.sol";

contract Todos {
   // An array of 'Todo' structs
   Todo[] public todos;
}