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Update docs (#2168)

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* Update docs for ERC20 and ERC721

* Add EnumerableMap to docs

* Update misc guides

* Apply suggestions from code review

Co-Authored-By: Francisco Giordano <frangio.1@gmail.com>

Co-authored-by: Francisco Giordano <frangio.1@gmail.com>
This commit is contained in:
Nicolás Venturo
2020-04-03 13:17:24 -03:00
committed by GitHub
parent 6668a4d05c
commit 402c6ab4cc
11 changed files with 53 additions and 69 deletions
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13
docs/modules/ROOT/pages/erc20.adoc
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@ -13,19 +13,18 @@ Here's what our GLD token might look like.
[source,solidity]
----
pragma solidity ^0.5.0;
pragma solidity ^0.6.0;
import "@openzeppelin/contracts/token/ERC20/ERC20.sol";
import "@openzeppelin/contracts/token/ERC20/ERC20Detailed.sol";
contract GLDToken is ERC20, ERC20Detailed {
constructor(uint256 initialSupply) ERC20Detailed("Gold", "GLD", 18) public {
contract GLDToken is ERC20 {
constructor(uint256 initialSupply) ERC20("Gold", "GLD") public {
_mint(msg.sender, initialSupply);
}
}
----
Our contracts are often used via https://solidity.readthedocs.io/en/latest/contracts.html#inheritance[inheritance], and here we're reusing xref:api:token/ERC20.adoc#erc20[`ERC20`] for the basic standard implementation and xref:api:token/ERC20.adoc#ERC20Detailed[`ERC20Detailed`] to get the xref:api:token/ERC20.adoc#ERC20Detailed-name--[`name`], xref:api:token/ERC20.adoc#ERC20Detailed-symbol--[`symbol`], and xref:api:token/ERC20.adoc#ERC20Detailed-decimals--[`decimals`] properties. Additionally, we're creating an `initialSupply` of tokens, which will be assigned to the address that deploys the contract.
Our contracts are often used via https://solidity.readthedocs.io/en/latest/contracts.html#inheritance[inheritance], and here we're reusing xref:api:token/ERC20.adoc#erc20[`ERC20`] for both the basic standard implementation and the xref:api:token/ERC20.adoc#ERC20-name--[`name`], xref:api:token/ERC20.adoc#ERC20-symbol--[`symbol`], and xref:api:token/ERC20.adoc#ERC20-decimals--[`decimals`] optional extensions. Additionally, we're creating an `initialSupply` of tokens, which will be assigned to the address that deploys the contract.
TIP: For a more complete discussion of ERC20 supply mechanisms, see xref:erc20-supply.adoc[Creating ERC20 Supply].
@ -53,7 +52,7 @@ We can also xref:api:token/ERC20.adoc#IERC20-transfer-address-uint256-[transfer]
Often, you'll want to be able to divide your tokens into arbitrary amounts: say, if you own `5 GLD`, you may want to send `1.5 GLD` to a friend, and keep `3.5 GLD` to yourself. Unfortunately, Solidity and the EVM do not support this behavior: only integer (whole) numbers can be used, which poses an issue. You may send `1` or `2` tokens, but not `1.5`.
To work around this, xref:api:token/ERC20.adoc#ERC20Detailed[`ERC20Detailed`] provides a xref:api:token/ERC20.adoc#ERC20Detailed-decimals--[`decimals`] field, which is used to specify how many decimal places a token has. To be able to transfer `1.5 GLD`, `decimals` must be at least `1`, since that number has a single decimal place.
To work around this, xref:api:token/ERC20.adoc#ERC20[`ERC20`] provides a xref:api:token/ERC20.adoc#ERC20-decimals--[`decimals`] field, which is used to specify how many decimal places a token has. To be able to transfer `1.5 GLD`, `decimals` must be at least `1`, since that number has a single decimal place.
How can this be achieved? It's actually very simple: a token contract can use larger integer values, so that a balance of `50` will represent `5 GLD`, a transfer of `15` will correspond to `1.5 GLD` being sent, and so on.
@ -61,6 +60,8 @@ It is important to understand that `decimals` is _only used for display purposes
You'll probably want to use a `decimals` value of `18`, just like Ether and most ERC20 token contracts in use, unless you have a very special reason not to. When minting tokens or transferring them around, you will be actually sending the number `num GLD * 10^decimals`.
NOTE: By default, `ERC20` uses a value of `18` for `decimals`. To use a different value, you will need to call xref:api:token/ERC20.adoc#ERC20-_setupDecimals-uint8-[_setupDecimals] in your constructor.
So if you want to send `5` tokens using a token contract with 18 decimals, the the method to call will actually be:
```solidity