ERC721.transferFrom

[tonimateos]

As an asset owner, I want to be able to execute ERC721.transferFrom, so I can transfer assets

Link to ERC721 standard, which specifies rules that must be checked by transferFrom - here

ACCEPTANCE

• I can execute contractAddress.transferFrom in a manner that fails unless the conditions defined by the ERC721 standard are met
• After successful execution, the method ownerOf returns the new owner.
• In this task: implemented as only non-payable, so if someone transfers money in the call, it reverts.

[magecnion]

Considerations and Thoughts Related to the Task

• transferFrom is only accessible when the action is performed through the precompiles module.
• When querying assetOwner from the runtime storage using, for example, the Polkadot.js client, the default initial owner logic is not applied because it is also part of the precompiles.
• The owner account_id used to store the mapping asset_id => owner in the runtime is the same as H160 (20 bytes), but it is extended to 32 bytes with zeros on the left. This means the account cannot be used to perform authenticated actions (e.g., we cannot verify that an extrinsic has been signed by such an account). We need to implement something similar to Moonbeam's unified accounts Moonbeam Unified Accounts.

[ghost]

Considerations and Thoughts Related to the Task

• transferFrom is only accessible when the action is performed through the precompiles module.
• When querying assetOwner from the runtime storage using, for example, the Polkadot.js client, the default initial owner logic is not applied because it is also part of the precompiles.
• The owner account_id used to store the mapping asset_id => owner in the runtime is the same as H160 (20 bytes), but it is extended to 32 bytes with zeros on the left. This means the account cannot be used to perform authenticated actions (e.g., we cannot verify that an extrinsic has been signed by such an account). We need to implement something similar to Moonbeam's unified accounts Moonbeam Unified Accounts.

1. yes, I think it's fine. We don't expose any extrinsic that can perform the transfer, so we should be safe on that regard as well.
2. correct. As I mentioned in the channel, one way to approach it is to have an RPC that can return the "correct" ownerOf by applying the logic that we apply in the precompiles. And this will be interface for Substrate clients
3. yes, exactly. I also think that we should have unified accounts.

[tonimateos]

QA: The logic works well (you can transfer only if you're the owner, the owner changes on transfer, etc), but the emitted Transfer event seems to contains a "tokenId" not related to the transferred tokenId