407 For Loop

2023/12/31閱讀時間約 9 分鐘

do something repeately

withdraw money

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.18;

import {PriceConverter} from "./PriceConverter.sol";

contract FundMe {
    using PriceConverter for uint256;

    uint256 public minimumUsd = 5e18;

    address[] public funders;
    mapping(address funder => uint256 amountFunded) public addressToAmountFunded;

    function fund() public payable {
        require(msg.value.getConversionRate() >= minimumUsd, "didn't send enought ETH");
        funders.push(msg.sender);
        addressToAmountFunded[msg.sender] = addressToAmountFunded[msg.sender] + msg.value;   
    }

    function withdraw() public {} 
        // for loop
        // [1, 2, 3, 4] elements
        //  0, 1, 2, 3  indexed
        // for(/* starting index, ending index, step amount */)
        for(uint256 funderIndex = 0; funderIndex < funders.length; funder Index++;){
            address funder = funders[funderIndex];
            addressToAmountFunded[funder] = 0;
        }
    }
}

resetting an array

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.18;

import {PriceConverter} from "./PriceConverter.sol";

contract FundMe {
    using PriceConverter for uint256;

    uint256 public minimumUsd = 5e18;

    address[] public funders;
    mapping(address funder => uint256 amountFunded) public addressToAmountFunded;

    function fund() public payable {
        require(msg.value.getConversionRate() >= minimumUsd, "didn't send enought ETH");
        funders.push(msg.sender);
        addressToAmountFunded[msg.sender] = addressToAmountFunded[msg.sender] + msg.value;   
    }

    function withdraw() public {} 
        // for loop
        // [1, 2, 3, 4] elements
        //  0, 1, 2, 3  indexed
        // for(/* starting index, ending index, step amount */)
        for(uint256 funderIndex = 0; funderIndex < funders.length; funder Index++;){
            address funder = funders[funderIndex];
            addressToAmountFunded[funder] = 0;
        }
        // reset the array
        funders = new address[](0);
        // withdaw the funds
    }
}

sending ETH from a contract

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.18;

import {PriceConverter} from "./PriceConverter.sol";

contract FundMe {
    using PriceConverter for uint256;

    uint256 public minimumUsd = 5e18;

    address[] public funders;
    mapping(address funder => uint256 amountFunded) public addressToAmountFunded;

    function fund() public payable {
        require(msg.value.getConversionRate() >= minimumUsd, "didn't send enought ETH");
        funders.push(msg.sender);
        addressToAmountFunded[msg.sender] = addressToAmountFunded[msg.sender] + msg.value;   
    }

    function withdraw() public {} 
        // for loop
        // [1, 2, 3, 4] elements
        //  0, 1, 2, 3  indexed
        // for(/* starting index, ending index, step amount */)
        for(uint256 funderIndex = 0; funderIndex < funders.length; funder Index++;){
            address funder = funders[funderIndex];
            addressToAmountFunded[funder] = 0;
        }
        // reset the array
        funders = new address[](0);
        // actually withdaw the funds
    
        // transfer the fund to whoever calling this withdraw function
        // msg.sender = address
        // payable(msg.sender) = payable address
        payable msg.sender.transfer(address(this).balance);
        
        // send
        bool sendSuccress = payable(msg.sender).send(address(this).balance);
        require(sendSuccress, "Send failed");
        // call
        (bool callSuccess, ) = payable(msg.sender).call{value: address(this).balance}("");
        require(callSuccess, "Call failed");
    }
}