FundMe in British pounds #1750

Vodvalex · 2024-05-24T16:27:25Z

Vodvalex
May 24, 2024

Dear All.Since I live in the UK I am trying to build a smart contract FundMe in British Pounds(GBP).but I am stuck.I have used the contract from chainlink data feed ''Getting a different price denomination:

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.7;

import {AggregatorV3Interface} from "@chainlink/contracts/src/v0.8/shared/interfaces/AggregatorV3Interface.sol";

/**

Network: Sepolia
Base: BTC/USD
Base Address: 0x1b44F3514812d835EB1BDB0acB33d3fA3351Ee43
Quote: EUR/USD
Quote Address: 0x1a81afB8146aeFfCFc5E50e8479e826E7D55b910
Decimals: 8
*/

/**

THIS IS AN EXAMPLE CONTRACT THAT USES HARDCODED VALUES FOR CLARITY.
THIS IS AN EXAMPLE CONTRACT THAT USES UN-AUDITED CODE.
DO NOT USE THIS CODE IN PRODUCTION.
*/

contract PriceConverter {
function getDerivedPrice(
address _base,
address _quote,
uint8 _decimals
) public view returns (int256) {
require(
_decimals > uint8(0) && _decimals <= uint8(18),
"Invalid _decimals"
);
int256 decimals = int256(10 ** uint256(_decimals));
(, int256 basePrice, , , ) = AggregatorV3Interface(_base)
.latestRoundData();
uint8 baseDecimals = AggregatorV3Interface(_base).decimals();
basePrice = scalePrice(basePrice, baseDecimals, _decimals);

    (, int256 quotePrice, , , ) = AggregatorV3Interface(_quote)
        .latestRoundData();
    uint8 quoteDecimals = AggregatorV3Interface(_quote).decimals();
    quotePrice = scalePrice(quotePrice, quoteDecimals, _decimals);

    return (basePrice * decimals) / quotePrice;
}

function scalePrice(
    int256 _price,
    uint8 _priceDecimals,
    uint8 _decimals
) internal pure returns (int256) {
    if (_priceDecimals < _decimals) {
        return _price * int256(10 ** uint256(_decimals - _priceDecimals));
    } else if (_priceDecimals > _decimals) {
        return _price / int256(10 ** uint256(_priceDecimals - _decimals));
    }
    return _price;
}

}

Now how to move to the function getConversionRate() from this point??? I suspect there should be some conversion function from int to uint or perhaps I am moving to the wrong direction. Sorry I am a beginner. Your help will be much apriciated.Thank you.

lucaliebenberg · 2024-05-24T17:20:58Z

lucaliebenberg
May 24, 2024

Hi @Vodvalex could you please provide some more context as to what it is you're stuck with?

Are you just needing to get the price feed in pounds and not dollars?

0 replies

EngrPips · 2024-05-25T04:41:29Z

EngrPips
May 25, 2024

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.7;

import {AggregatorV3Interface} from "@chainlink/contracts/src/v0.8/shared/interfaces/AggregatorV3Interface.sol";

/**

Network: Sepolia
Base: BTC/USD
Base Address: 0x1b44F3514812d835EB1BDB0acB33d3fA3351Ee43
Quote: EUR/USD
Quote Address: 0x1a81afB8146aeFfCFc5E50e8479e826E7D55b910
Decimals: 8
*/
/**

THIS IS AN EXAMPLE CONTRACT THAT USES HARDCODED VALUES FOR CLARITY.
THIS IS AN EXAMPLE CONTRACT THAT USES UN-AUDITED CODE.
DO NOT USE THIS CODE IN PRODUCTION.
*/
contract PriceConverter {
function getDerivedPrice(
address _base,
address _quote,
uint8 _decimals
) public view returns (int256) {
require(
_decimals > uint8(0) && _decimals <= uint8(18),
"Invalid _decimals"
);
int256 decimals = int256(10 ** uint256(_decimals));
(, int256 basePrice, , , ) = AggregatorV3Interface(_base)
.latestRoundData();
uint8 baseDecimals = AggregatorV3Interface(_base).decimals();
basePrice = scalePrice(basePrice, baseDecimals, _decimals);

    (, int256 quotePrice, , , ) = AggregatorV3Interface(_quote)
        .latestRoundData();
    uint8 quoteDecimals = AggregatorV3Interface(_quote).decimals();
    quotePrice = scalePrice(quotePrice, quoteDecimals, _decimals);

    return (basePrice * decimals) / quotePrice;
}

function scalePrice(
    int256 _price,
    uint8 _priceDecimals,
    uint8 _decimals
) internal pure returns (int256) {
    if (_priceDecimals < _decimals) {
        return _price * int256(10 ** uint256(_decimals - _priceDecimals));
    } else if (_priceDecimals > _decimals) {
        return _price / int256(10 ** uint256(_priceDecimals - _decimals));
    }
    return _price;
}
}

1 reply

EngrPips May 25, 2024

Hello @Vodvalex, Please describe in full detail the actual issue. Are you getting the wrong price? What is the issue you are having?

Vodvalex · 2024-05-30T15:12:42Z

Vodvalex
May 30, 2024
Author

Hi Everyone.Thanks for your replies.My deepest appologies I have been offshore for 1 week and could not answer.I have done the following :
PriceConverterGBP.sol

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.18;
import {AggregatorV3Interface} from "@chainlink/contracts/src/v0.8/interfaces/AggregatorV3Interface.sol";

/**

Network: Sepolia
Base: ETH/USD
Base Address: 0x694AA1769357215DE4FAC081bf1f309aDC325306
Quote: EUR/USD
Quote Address: 0x635A86F9fdD16Ff09A0701C305D3a845F1758b8E
Decimals: 8
*/

/**

THIS IS AN EXAMPLE CONTRACT THAT USES HARDCODED VALUES FOR CLARITY.
THIS IS AN EXAMPLE CONTRACT THAT USES UN-AUDITED CODE.
DO NOT USE THIS CODE IN PRODUCTION.
*/

library PriceConverterGBP {
function getGbpPrice(
address _base,
address _quote,
uint8 _decimals
) public view returns (int256) {
require(
_decimals > uint8(0) && _decimals <= uint8(18),
"Invalid _decimals"
);
int256 decimals = int256(10 ** uint256(_decimals));
(, int256 basePrice, , , ) = AggregatorV3Interface(_base)
.latestRoundData();
uint8 baseDecimals = AggregatorV3Interface(_base).decimals();
basePrice = scalePrice(basePrice, baseDecimals, _decimals);

    (, int256 quotePrice, , , ) = AggregatorV3Interface(_quote)
        .latestRoundData();
    uint8 quoteDecimals = AggregatorV3Interface(_quote).decimals();
    quotePrice = scalePrice(quotePrice, quoteDecimals, _decimals);

    return  (((basePrice * decimals) / quotePrice)*1e10);
}

function scalePrice(
    int256 _price,
    uint8 _priceDecimals,
    uint8 _decimals
) internal pure returns (int256) {
    if (_priceDecimals < _decimals) {
        return _price * int256(10 ** uint256(_decimals - _priceDecimals));
    } else if (_priceDecimals > _decimals) {
        return _price / int256(10 ** uint256(_priceDecimals - _decimals));
    }
    return _price;
}

function getConversionRate(int ethamount) internal view returns (int){
    address _base= 0x694AA1769357215DE4FAC081bf1f309aDC325306;
    address _quote=0x635A86F9fdD16Ff09A0701C305D3a845F1758b8E;
    uint8 _decimals=8;
    int ethPriceGbp=  (getGbpPrice (_base, _quote, _decimals));
    
    int ethAmountGbp= (ethPriceGbp*ethamount)/1e18;
    return ethAmountGbp;

}

}

FundMeGBP.sol

/ /SPDX-License-Identifier: MIT
pragma solidity ^0.8.18;
import {AggregatorV3Interface} from "@chainlink/contracts/src/v0.8/interfaces/AggregatorV3Interface.sol";
import {PriceConverterGBP} from "PriceConverterGBP.sol";

contract FundMeGBP{
using PriceConverterGBP for uint;

uint public constant SERVICE_FEE =5e18;
address [] private s_customers;
address private immutable i_owner; 
AggregatorV3Interface private s_priceFeed;



mapping( address => uint) private s_addressToAmountPay;


 function Fund () public payable {
    require ( msg.value >= SERVICE_FEE, "You need to spend more ETH!"); 
    s_customers.push(msg.sender);
    s_addressToAmountPaid[msg.sender]+= msg.value;
    
   }

}

At this stage I am the most interested in the "require ( msg.value >= SERVICE_FEE, "You need to spend more ETH!"); " in function fund() in order for me to create my Smart contract in GBP. I am sure a lot of you have been much longer in this game than me.If anyone could possibly kindly check what I have done and perhaps point out on my mistakes that would be great.Then I will start testing it in Foundry.Thank you.

0 replies

EngrPips · 2024-05-30T16:41:34Z

EngrPips
May 30, 2024

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.18;
import {AggregatorV3Interface} from "@chainlink/contracts/src/v0.8/interfaces/AggregatorV3Interface.sol";

/**

Network: Sepolia
Base: ETH/USD
Base Address: 0x694AA1769357215DE4FAC081bf1f309aDC325306
Quote: EUR/USD
Quote Address: 0x635A86F9fdD16Ff09A0701C305D3a845F1758b8E
Decimals: 8
*/
/**

THIS IS AN EXAMPLE CONTRACT THAT USES HARDCODED VALUES FOR CLARITY.
THIS IS AN EXAMPLE CONTRACT THAT USES UN-AUDITED CODE.
DO NOT USE THIS CODE IN PRODUCTION.
*/
library PriceConverterGBP {
function getGbpPrice(
address _base,
address _quote,
uint8 _decimals
) public view returns (int256) {
require(
_decimals > uint8(0) && _decimals <= uint8(18),
"Invalid _decimals"
);
int256 decimals = int256(10 ** uint256(_decimals));
(, int256 basePrice, , , ) = AggregatorV3Interface(_base)
.latestRoundData();
uint8 baseDecimals = AggregatorV3Interface(_base).decimals();
basePrice = scalePrice(basePrice, baseDecimals, _decimals);

    (, int256 quotePrice, , , ) = AggregatorV3Interface(_quote)
        .latestRoundData();
    uint8 quoteDecimals = AggregatorV3Interface(_quote).decimals();
    quotePrice = scalePrice(quotePrice, quoteDecimals, _decimals);

    return  (((basePrice * decimals) / quotePrice)*1e10);
}

function scalePrice(
    int256 _price,
    uint8 _priceDecimals,
    uint8 _decimals
) internal pure returns (int256) {
    if (_priceDecimals < _decimals) {
        return _price * int256(10 ** uint256(_decimals - _priceDecimals));
    } else if (_priceDecimals > _decimals) {
        return _price / int256(10 ** uint256(_priceDecimals - _decimals));
    }
    return _price;
}

function getConversionRate(int ethamount) internal view returns (int){
    address _base= 0x694AA1769357215DE4FAC081bf1f309aDC325306;
    address _quote=0x635A86F9fdD16Ff09A0701C305D3a845F1758b8E;
    uint8 _decimals=8;
    int ethPriceGbp=  (getGbpPrice (_base, _quote, _decimals));
    
    int ethAmountGbp= (ethPriceGbp*ethamount)/1e18;
    return ethAmountGbp;

}
}

0 replies

EngrPips · 2024-05-30T16:42:21Z

EngrPips
May 30, 2024

/ /SPDX-License-Identifier: MIT
pragma solidity ^0.8.18;
import {AggregatorV3Interface} from "@chainlink/contracts/src/v0.8/interfaces/AggregatorV3Interface.sol";
import {PriceConverterGBP} from "PriceConverterGBP.sol";

contract FundMeGBP{
using PriceConverterGBP for uint;

uint public constant SERVICE_FEE =5e18;
address [] private s_customers;
address private immutable i_owner; 
AggregatorV3Interface private s_priceFeed;



mapping( address => uint) private s_addressToAmountPay;


 function Fund () public payable {
    require ( msg.value >= SERVICE_FEE, "You need to spend more ETH!"); 
    s_customers.push(msg.sender);
    s_addressToAmountPaid[msg.sender]+= msg.value;
    
   }  
}

0 replies

EngrPips · 2024-05-30T16:43:45Z

EngrPips
May 30, 2024

#1750.

So what is wrong with the line "require ( msg.value >= SERVICE_FEE, "You need to spend more ETH!"); ?

4 replies

Vodvalex May 31, 2024
Author

I am bit concern that in the course for USD it is a clear indication that msg.value is attached to getConversionRate:
require(msg.value.getConversionRate(s_priceFeed).... wether in my case it is just msg.value.When I try to add getConversionRate : require(msg.value.getConversionRate... from PriceConverterGBP it comes up with error and does not compile.So it seems to me there is some link is missing in the latter case .So the question is why with USD IT IS :
require(msg.value.getConversionRate(s_priceFeed)......., but in GBP:
require ( msg.value..... with no getConversionRate?

EngrPips May 31, 2024

Hello @Vodvalex, In your PriceConverter Library, you told your getConversionRate function to expect the type of int but in your FundMeGBP contract you declare the PriceConverter to be used for uint and then you are trying to pass msg.sender which is a uint256 to the getConversionRate function which you clearly told to expect a type of int. So it makes sense that it doesn't work.

function getConversionRate(int ethamount) internal view returns (int){
    address _base= 0x694AA1769357215DE4FAC081bf1f309aDC325306;
    address _quote=0x635A86F9fdD16Ff09A0701C305D3a845F1758b8E;
    uint8 _decimals=8;
    int ethPriceGbp=  (getGbpPrice (_base, _quote, _decimals));
    
    int ethAmountGbp= (ethPriceGbp*ethamount)/1e18;
    return ethAmountGbp;

}

Vodvalex Jun 1, 2024
Author

Ah yes.Thanks for pointing it out.Thank you for your help

EngrPips Jun 1, 2024

You are welcome; keep crushing it!

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