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openzeppelin-contracts/contracts/token/ERC721
Nicolás Venturo 5dfe7215a9 Migrate Contracts to Solidity v0.6 (#2080)
* Initial migration to Solidity 0.6.x - v3.0 first steps (#2063)

* Initial migration, missing GSN, 721, 777 and Crowdsales.

* Add _beforeTokenOperation and _afterTokenOperation.

* Add documentation for hooks.

* Add hooks doc

* Add missing drafts

* Add back ERC721 with hooks

* Bring back ERC777

* Notes on hooks

* Bring back GSN

* Make functions virtual

* Make GSN overrides explicit

* Fix ERC20Pausable tests

* Remove virtual from some view functions

* Update linter

* Delete examples

* Remove unnecessary virtual

* Remove roles from Pausable

* Remove roles

* Remove users of roles

* Adapt ERC20 tests

* Fix ERC721 tests

* Add all ERC721 hooks

* Add ERC777 hooks

* Fix remaining tests

* Bump compiler version

* Move 721BurnableMock into mocks directory

* Remove _before hooks

* Fix tests

* Upgrade linter

* Put modifiers last

* Remove _beforeTokenApproval and _beforeOperatorApproval hooks
2020-02-14 11:12:32 -03:00
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= ERC 721

This set of interfaces, contracts, and utilities are all related to the https://eips.ethereum.org/EIPS/eip-721[ERC721 Non-Fungible Token Standard].

TIP: For a walkthrough on how to create an ERC721 token read our xref:ROOT:tokens.adoc#ERC721[ERC721 guide].

The EIP consists of three interfaces, found here as {IERC721}, {IERC721Metadata}, and {IERC721Enumerable}. Only the first one is required in a contract to be ERC721 compliant.

Each interface is implemented separately in {ERC721}, {ERC721Metadata}, and {ERC721Enumerable}. You can choose the subset of functionality you would like to support in your token by combining the
desired subset through inheritance.

The fully featured token implementing all three interfaces is prepackaged as {ERC721Full}.

Additionally, {IERC721Receiver} can be used to prevent tokens from becoming forever locked in contracts. Imagine sending an in-game item to an exchange address that can't send it back!. When using <<IERC721-safeTransferFrom,`safeTransferFrom`>>, the token contract checks to see that the receiver is an {IERC721Receiver}, which implies that it knows how to handle {ERC721} tokens. If you're writing a contract that needs to receive {ERC721} tokens, you'll want to include this interface.

Finally, some custom extensions are also included:

* {ERC721Mintable} — like the ERC20 version, this allows certain addresses to mint new tokens
* {ERC721Pausable} — like the ERC20 version, this allows addresses to freeze transfers of tokens

NOTE: This page is incomplete. We're working to improve it for the next release. Stay tuned!

== Core

{{IERC721}}

{{ERC721}}

{{IERC721Metadata}}

{{ERC721Metadata}}

{{ERC721Enumerable}}

{{IERC721Enumerable}}

{{IERC721Full}}

{{ERC721Full}}

{{IERC721Receiver}}

== Extensions

{{ERC721Mintable}}

{{ERC721MetadataMintable}}

{{ERC721Burnable}}

{{ERC721Pausable}}

== Convenience

{{ERC721Holder}}