ERC721Upgradeable multiple upgrades

[abcoathup]

Hi @SrChong,

@abcoathup

I am not sure about how arrays are stored, so I assume you won’t be able to add any fields to your struct.

It is not upgrade safe to add fields to a struct being used in an array.

@SrChong

And according to the next page writing-upgradeable if i only deploy BoxV1 twice, the second time i deployed, i only need leave the variables, remove all new functions, and user override or write new functions…

Implementation contracts can be stand alone or they can inherit from previous versions of the implementation contract. It is up to you for what works for your use case.

I tend to use stand alone. I only used inheritance as an example here.

OpenZeppelin Upgrades: Step by Step Tutorial for Truffle shows an example of implementation contracts not inheriting from previous versions.