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Fix guides for 5.0 (#4654)

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Co-authored-by: Ernesto García <ernestognw@gmail.com>
(cherry picked from commit e12511b53e)
This commit is contained in:
Francisco
2023-10-04 22:37:11 -03:00
committed by Francisco Giordano
parent 228013d232
commit bd25a0a26f
7 changed files with 50 additions and 94 deletions
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21
docs/modules/ROOT/pages/access-control.adoc
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@ -9,24 +9,9 @@ The most common and basic form of access control is the concept of _ownership_:
OpenZeppelin Contracts provides xref:api:access.adoc#Ownable[`Ownable`] for implementing ownership in your contracts.
[source,solidity]
----
// contracts/MyContract.sol
// SPDX-License-Identifier: MIT
pragma solidity ^0.8.20;
import {Ownable} from "@openzeppelin/contracts/access/Ownable.sol";
contract MyContract is Ownable {
function normalThing() public {
// anyone can call this normalThing()
}
function specialThing() public onlyOwner {
// only the owner can call specialThing()!
}
}
----
```solidity
include::api:example$MyContractOwnable.sol[]
```
By default, the xref:api:access.adoc#Ownable-owner--[`owner`] of an `Ownable` contract is the account that deployed it, which is usually exactly what you want.

24
docs/modules/ROOT/pages/erc20-supply.adoc
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@ -57,27 +57,13 @@ As we can see, `_mint` makes it super easy to do this correctly.
[[automating-the-reward]]
== Automating the Reward
So far our supply mechanism was triggered manually, but `ERC20` also allows us to extend the core functionality of the token through the xref:api:token/ERC20.adoc#ERC20-_beforeTokenTransfer-address-address-uint256-[`_beforeTokenTransfer`] hook (see xref:extending-contracts.adoc#using-hooks[Using Hooks]).
So far our supply mechanism was triggered manually, but `ERC20` also allows us to extend the core functionality of the token through the xref:api:token/ERC20.adoc#ERC20-_update-address-address-uint256-[`_update`] function.
Adding to the supply mechanism from the previous section, we can use this hook to mint a miner reward for every token transfer that is included in the blockchain.
Adding to the supply mechanism from the previous section, we can use this function to mint a miner reward for every token transfer that is included in the blockchain.
[source,solidity]
----
contract ERC20WithAutoMinerReward is ERC20 {
constructor() ERC20("Reward", "RWD") {}
function _mintMinerReward() internal {
_mint(block.coinbase, 1000);
}
function _beforeTokenTransfer(address from, address to, uint256 value) internal virtual override {
if (!(from == address(0) && to == block.coinbase)) {
_mintMinerReward();
}
super._beforeTokenTransfer(from, to, value);
}
}
----
```solidity
include::api:example$ERC20WithAutoMinerReward.sol[]
```
[[wrapping-up]]
== Wrapping Up

54
docs/modules/ROOT/pages/extending-contracts.adoc
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@ -68,60 +68,6 @@ The `super.revokeRole` statement at the end will invoke ``AccessControl``'s orig
NOTE: The same rule is implemented and extended in xref:api:access.adoc#AccessControlDefaultAdminRules[`AccessControlDefaultAdminRules`], an extension that also adds enforced security measures for the `DEFAULT_ADMIN_ROLE`.
[[using-hooks]]
== Using Hooks
Sometimes, in order to extend a parent contract you will need to override multiple related functions, which leads to code duplication and increased likelihood of bugs.
For example, consider implementing safe xref:api:token/ERC20.adoc#ERC20[`ERC20`] transfers in the style of xref:api:token/ERC721.adoc#IERC721Receiver[`IERC721Receiver`]. You may think overriding xref:api:token/ERC20.adoc#ERC20-transfer-address-uint256-[`transfer`] and xref:api:token/ERC20.adoc#ERC20-transferFrom-address-address-uint256-[`transferFrom`] would be enough, but what about xref:api:token/ERC20.adoc#ERC20-_transfer-address-address-uint256-[`_transfer`] and xref:api:token/ERC20.adoc#ERC20-_mint-address-uint256-[`_mint`]? To prevent you from having to deal with these details, we introduced **hooks**.
Hooks are simply functions that are called before or after some action takes place. They provide a centralized point to _hook into_ and extend the original behavior.
Here's how you would implement the `IERC721Receiver` pattern in `ERC20`, using the xref:api:token/ERC20.adoc#ERC20-_beforeTokenTransfer-address-address-uint256-[`_beforeTokenTransfer`] hook:
```solidity
pragma solidity ^0.8.20;
import {ERC20} from "@openzeppelin/contracts/token/ERC20/ERC20.sol";
contract ERC20WithSafeTransfer is ERC20 {
function _beforeTokenTransfer(address from, address to, uint256 amount)
internal virtual override
{
super._beforeTokenTransfer(from, to, amount);
require(_validRecipient(to), "ERC20WithSafeTransfer: invalid recipient");
}
function _validRecipient(address to) private view returns (bool) {
...
}
...
}
```
Using hooks this way leads to cleaner and safer code, without having to rely on a deep understanding of the parent's internals.
=== Rules of Hooks
There's a few guidelines you should follow when writing code that uses hooks in order to prevent issues. They are very simple, but do make sure you follow them:
1. Whenever you override a parent's hook, re-apply the `virtual` attribute to the hook. That will allow child contracts to add more functionality to the hook.
2. **Always** call the parent's hook in your override using `super`. This will make sure all hooks in the inheritance tree are called: contracts like xref:api:token/ERC20.adoc#ERC20Pausable[`ERC20Pausable`] rely on this behavior.
```solidity
contract MyToken is ERC20 {
function _beforeTokenTransfer(address from, address to, uint256 amount)
internal virtual override // Add virtual here!
{
super._beforeTokenTransfer(from, to, amount); // Call parent hook
...
}
}
```
That's it! Enjoy simpler code using hooks!
== Security
The maintainers of OpenZeppelin Contracts are mainly concerned with the correctness and security of the code as published in the library, and the combinations of base contracts with the official extensions from the library.