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Automatically merged updates to draft EIP(s) 2535 (#3173)

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 - It only modifies existing Draft or Last Call EIP(s)
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Nick Mudge 2020-12-22 19:29:25 -05:00 committed by GitHub
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19
EIPS/eip-2535.md
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@ -107,16 +107,13 @@ A diamond can be upgraded if it has a diamondCut external function or other func
A facet defines external functions and can define or use internal functions, libraries, and state variables.
A facet can declare and use state variables but it does it in a way that is safer, easier and more flexible for diamonds.
Facet state variables are declared in structs. Each struct is given a specific position in contract storage. This technique is called **Diamond Storage**.
A facet can declare state variables in structs. Each struct is given a specific position in contract storage. This technique is called **Diamond Storage**.
Here is a simple example that shows diamond storage and its use in a facet:
```Solidity
// A contract that implements diamond storage.
// This contract is inherited and used by facets.
contract DiamondStorageContract {
library LibA {
// This struct contains state variables we care about.
struct DiamondStorage {
@ -128,23 +125,23 @@ contract DiamondStorageContract {
// ds is short for DiamondStorage
function diamondStorage() internal pure returns(DiamondStorage storage ds) {
// Specifies a random position from a hash of a string
bytes32 storagePosition = keccak256("diamond.storage")
bytes32 storagePosition = keccak256("diamond.storage.LibA")
// Set the position of our struct in contract storage
assembly {ds.slot := storagePosition}
}
}
// Our facet inherits and uses the diamond storage defined above.
contract FacetA is DiamondStorageContract {
// Our facet uses the diamond storage defined above.
contract FacetA {
function setDataA(bytes32 _dataA) external {
DiamondStorage storage ds = diamondStorage();
LibA.DiamondStorage storage ds = LibA.diamondStorage();
require(ds.owner == msg.sender, "Must be owner.");
ds.dataA = _dataA
}
function getDataA() external view returns (bytes32) {
return diamondStorage().dataA
return LibDiamond.diamondStorage().dataA
}
}
```
@ -155,8 +152,6 @@ By using diamond storage facets can declare their own state variables that do no
By using diamond storage facets can be developed independently, without connection or concern for other facets.
Solidity libraries can also use diamond storage.
## Diamonds Can Use Other Contract Storage Strategies
Diamonds and facets don't have to use diamond storage. They can use other contract storage strategies such as contract inheritance.