sending-ether/index.html

<!DOCTYPE html><html class="fa-events-icons-ready" lang="en"><head><meta charset="utf-8"><link href="/favicon.ico" rel="shortcut icon"><meta content="width=device-width,initial-scale=1,shrink-to-fit=yes" name="viewport"><meta content="#000000" name="theme-color"><script src="https://www.google-analytics.com/analytics.js" async type="text/javascript"></script><script src="https://use.fontawesome.com/ba3dde78ee.js"></script><link href="https://www.googletagmanager.com" rel="preconnect"><link href="https://use.fontawesome.com/ba3dde78ee.css" rel="stylesheet" media="all"><link href="/manifest.json" rel="manifest"><title>Sending Ether (transfer, send, call) | Solidity by Example | 0.7.6</title><script src="https://www.googletagmanager.com/gtag/js?id=UA-133759045-1" async></script><script>function gtag(){dataLayer.push(arguments)}window.dataLayer=window.dataLayer||[],gtag("js",new Date),gtag("config","UA-133759045-1")</script><link href="/static/css/2.8a5f298e.chunk.css" rel="stylesheet"><link href="/static/css/main.b19412ac.chunk.css" rel="stylesheet"><link href="https://use.fontawesome.com" rel="preconnect"><meta content="An example of sending Ether in Solidity" name="Description" data-react-helmet="true"><link href="https://www.google-analytics.com" rel="preconnect"></head><body><noscript>You need to enable JavaScript to run this app.</noscript><div id="root"><div class="App_component__1dd61"><div class="Header_component__1tkkW"><a href="/"><img alt="logo" class="Header_logo__2ins2" src="/static/media/logo.9a07f18c.svg"></a><h3 class="Header_header__3mObx"><a href="/">Solidity by Example</a><div class="Header_versions__eOBao"><div class="Header_version__1QJXf">version 0.7.6</div></div></h3></div><div class="App_main__3ZkGI"><div class="Example_component__mzuGC"><div class="Example_content__3-AiU"><h2>Sending Ether (transfer, send, call)</h2><div><h3 id="how-to-send-ether">How to send Ether?</h3><p>You can send Ether to other contracts by</p><ul><li><code>transfer</code> (2300 gas, throws error)</li><li><code>send</code> (2300 gas, returns bool)</li><li><code>call</code> (forward all gas or set gas, returns bool)</li></ul><h3 id="how-to-receive-ether">How to receive Ether?</h3><p>A contract receiving Ether must have at least one of the functions below</p><ul><li><code>receive() external payable</code></li><li><code>fallback() external payable</code></li></ul><p><code>receive()</code> is called if <code>msg.data</code> is empty, otherwise <code>fallback()</code> is called.</p><h3 id="which-method-should-you-use">Which method should you use?</h3><p><code>call</code> in combination with re-entrancy guard is the recommended method to use after December 2019.</p><p>Guard against re-entrancy by</p><ul><li>making all state changes before calling other contracts</li><li>using re-entrancy guard modifier</li></ul><pre><code class="language-solidity"><span class="hljs-comment">// SPDX-License-Identifier: MIT</span>
<span class="hljs-meta"><span class="hljs-keyword">pragma</span> <span class="hljs-keyword">solidity</span> ^0.7.6;</span>

<span class="hljs-class"><span class="hljs-keyword">contract</span> <span class="hljs-title">ReceiveEther</span> </span>{
    <span class="hljs-comment">/*
    Which function is called, fallback() or receive()?

           send Ether
               |
         msg.data is empty?
              / \
            yes  no
            /     \
receive() exists?  fallback()
         /   \
        yes   no
        /      \
    receive()   fallback()
    */</span>

    <span class="hljs-comment">// Function to receive Ether. msg.data must be empty</span>
    <span class="hljs-keyword">receive</span>() <span class="hljs-keyword">external</span> <span class="hljs-keyword">payable</span> {}

    <span class="hljs-comment">// Fallback function is called when msg.data is not empty</span>
    <span class="hljs-keyword">fallback</span>() <span class="hljs-keyword">external</span> <span class="hljs-keyword">payable</span> {}

    <span class="hljs-function"><span class="hljs-keyword">function</span> <span class="hljs-title">getBalance</span>(<span class="hljs-params"></span>) <span class="hljs-title"><span class="hljs-keyword">public</span></span> <span class="hljs-title"><span class="hljs-keyword">view</span></span> <span class="hljs-title"><span class="hljs-keyword">returns</span></span> (<span class="hljs-params"><span class="hljs-keyword">uint</span></span>) </span>{
        <span class="hljs-keyword">return</span> <span class="hljs-keyword">address</span>(<span class="hljs-built_in">this</span>).<span class="hljs-built_in">balance</span>;
    }
}

<span class="hljs-class"><span class="hljs-keyword">contract</span> <span class="hljs-title">SendEther</span> </span>{
    <span class="hljs-function"><span class="hljs-keyword">function</span> <span class="hljs-title">sendViaTransfer</span>(<span class="hljs-params"><span class="hljs-keyword">address</span> <span class="hljs-keyword">payable</span> _to</span>) <span class="hljs-title"><span class="hljs-keyword">public</span></span> <span class="hljs-title"><span class="hljs-keyword">payable</span></span> </span>{
        <span class="hljs-comment">// This function is no longer recommended for sending Ether.</span>
        _to.<span class="hljs-built_in">transfer</span>(<span class="hljs-built_in">msg</span>.<span class="hljs-built_in">value</span>);
    }

    <span class="hljs-function"><span class="hljs-keyword">function</span> <span class="hljs-title">sendViaSend</span>(<span class="hljs-params"><span class="hljs-keyword">address</span> <span class="hljs-keyword">payable</span> _to</span>) <span class="hljs-title"><span class="hljs-keyword">public</span></span> <span class="hljs-title"><span class="hljs-keyword">payable</span></span> </span>{
        <span class="hljs-comment">// Send returns a boolean value indicating success or failure.</span>
        <span class="hljs-comment">// This function is not recommended for sending Ether.</span>
        <span class="hljs-keyword">bool</span> sent = _to.<span class="hljs-built_in">send</span>(<span class="hljs-built_in">msg</span>.<span class="hljs-built_in">value</span>);
        <span class="hljs-built_in">require</span>(sent, <span class="hljs-string">"Failed to send Ether"</span>);
    }

    <span class="hljs-function"><span class="hljs-keyword">function</span> <span class="hljs-title">sendViaCall</span>(<span class="hljs-params"><span class="hljs-keyword">address</span> <span class="hljs-keyword">payable</span> _to</span>) <span class="hljs-title"><span class="hljs-keyword">public</span></span> <span class="hljs-title"><span class="hljs-keyword">payable</span></span> </span>{
        <span class="hljs-comment">// Call returns a boolean value indicating success or failure.</span>
        <span class="hljs-comment">// This is the current recommended method to use.</span>
        (<span class="hljs-keyword">bool</span> sent, <span class="hljs-keyword">bytes</span> <span class="hljs-keyword">memory</span> data) = _to.<span class="hljs-built_in">call</span>{<span class="hljs-built_in">value:</span> <span class="hljs-built_in">msg</span>.<span class="hljs-built_in">value</span>}(<span class="hljs-string">""</span>);
        <span class="hljs-built_in">require</span>(sent, <span class="hljs-string">"Failed to send Ether"</span>);
    }
}
</code></pre></div><p>Try on <a href="https://remix.ethereum.org" target="__blank">Remix</a></p></div></div></div><div class="App_footer__29Fsv"><div class="Footer_component__2wm-B"><div class="Footer_row__3cluQ">Donate<span aria-label="smiley" role="img">🙂</span></div><div class="Footer_row__3cluQ"><a href="https://etherscan.io/address/0x95a647B3d8a3F11176BAdB799b9499C671fa243a" target="__blank">0x95a6...fa243</a></div><div class="Footer_row__3cluQ">your ETH will directly go to<a href="https://khanacademy.org" target="__blank" class="Footer_khan__3lTcL">Khan Academy</a></div><div class="Footer_row__3cluQ"><a href="mailto:contact@solidity-by-example.org">contact@solidity-by-example.org</a></div><div class="Footer_row__3cluQ"><a href="https://github.com/solidity-by-example/solidity-by-example.github.io" target="__blank">source</a><div class="Footer_bar__93usQ">|</div><a href="https://github.com/solidity-by-example/solidity-by-example.github.io/blob/gh-pages/LICENSE" target="__blank">license</a></div></div></div></div></div><script>!function(e){function t(t){for(var n,l,i=t[0],a=t[1],p=t[2],c=0,s=[];c<i.length;c++)l=i[c],Object.prototype.hasOwnProperty.call(o,l)&&o[l]&&s.push(o[l][0]),o[l]=0;for(n in a)Object.prototype.hasOwnProperty.call(a,n)&&(e[n]=a[n]);for(f&&f(t);s.length;)s.shift()();return u.push.apply(u,p||[]),r()}function r(){for(var e,t=0;t<u.length;t++){for(var r=u[t],n=!0,i=1;i<r.length;i++){var a=r[i];0!==o[a]&&(n=!1)}n&&(u.splice(t--,1),e=l(l.s=r[0]))}return e}var n={},o={1:0},u=[];function l(t){if(n[t])return n[t].exports;var r=n[t]={i:t,l:!1,exports:{}};return e[t].call(r.exports,r,r.exports,l),r.l=!0,r.exports}l.m=e,l.c=n,l.d=function(e,t,r){l.o(e,t)||Object.defineProperty(e,t,{enumerable:!0,get:r})},l.r=function(e){"undefined"!=typeof Symbol&&Symbol.toStringTag&&Object.defineProperty(e,Symbol.toStringTag,{value:"Module"}),Object.defineProperty(e,"__esModule",{value:!0})},l.t=function(e,t){if(1&t&&(e=l(e)),8&t)return e;if(4&t&&"object"==typeof e&&e&&e.__esModule)return e;var r=Object.create(null);if(l.r(r),Object.defineProperty(r,"default",{enumerable:!0,value:e}),2&t&&"string"!=typeof e)for(var n in e)l.d(r,n,function(t){return e[t]}.bind(null,n));return r},l.n=function(e){var t=e&&e.__esModule?function(){return e.default}:function(){return e};return l.d(t,"a",t),t},l.o=function(e,t){return Object.prototype.hasOwnProperty.call(e,t)},l.p="/";var i=this["webpackJsonpsolidity-by-example"]=this["webpackJsonpsolidity-by-example"]||[],a=i.push.bind(i);i.push=t,i=i.slice();for(var p=0;p<i.length;p++)t(i[p]);var f=a;r()}([])</script><script src="/static/js/2.2c6f9866.chunk.js"></script><script src="/static/js/main.7645568c.chunk.js"></script></body></html>