This project is all about how to create contract factory. It means how to deploy contract from other contract on block chain. other aspect it touches are inheritance and override functions.
read the comments in code to understand it.
- Contract factory
to store newly create contracts from factory first create a variable of type contract that we've to generate.
SimpleStorage[] public simpleStorageArray;
So in StorageFactory file we want to generate many contracts of SimpleStorage so we declare a variable of type SimpleStorage[]. and give it a name simpleStorageArray
next, in createSimpleStorageContract method we're creating a contract using new keyword and store into simpleStorageArray variable so in future we can get address of any contract by it's index for that we've one more getter method that is by default created because simpleStorageArray visibility is public.
- inheritance
import "./SimpleStorage.sol";
syntax is
contract ExtraStorage is SimpleStorage
inheritance means get access to methods and properties of partent contract. here we're inheriting SimpleStorage contract into ExtraStorage means ExtraStorage contract can access all the methods from it's parent contract SimpleStorage.
- overrideing funtion
in parent contract we've to declare virtual keyword with function to which we wanted to override by child contract. in SimpleStroage contract we've mention virtual keyword with store method means any child contract can override only this method and can update the method as per needed not any other methods. in child contract when we override this method we've to mention override keyword.
here on the ExtraStorage contranct we mentioned both keywords virtual and override. it means we're overriding this menthod from parent contract and any child contract of ExtraStorage contract can also override this menthod.