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<divclass="breadcrumbs"><ahref="/v5/">Documentation</a> » <ahref="/v5/migration/">Migration Guide</a> » <spanclass="current">Migration: From Ethers v4</span></div>
<aname="migration-v4"></a><aname="migration-v4"></a><h1class="show-anchors"><div>Migration: From Ethers v4<divclass="anchors"><aclass="self"href="/v5/migration/ethers-v4/#migration-v4"></a></div></div></h1><p>This document only covers the features present in v4 which have changed in some important way in v5.</p>
<p>It does not cover all the new additional features that have been added and mainly aims to help those updating their older scripts and applications to retain functional parity.</p>
<aname="migration-v4--bignumber--namespace"></a><h3class="show-anchors"><div>Namespace<divclass="anchors"><aclass="self"href="/v5/migration/ethers-v4/#migration-v4--bignumber--namespace"></a></div></div></h3><p>Since <ahref="/v5/api/utils/bignumber/">BigNumber</a> is used quite frequently, it has been moved to the top level of the umbrella package.</p>
</div><aname="migration-v4--bignumber--creating-instances"></a><h3class="show-anchors"><div>Creating Instances<divclass="anchors"><aclass="self"href="/v5/migration/ethers-v4/#migration-v4--bignumber--creating-instances"></a></div></div></h3><p>The <codeclass="inline">bigNumberify</code> method was always preferred over the constructor since it could short-circuit an object instantiation for [[BigNumber] objects (since they are immutable). This has been moved to a static <codeclass="inline">from</code> class method.</p>
<aname="migration-v4--contracts--ens-name-resolution"></a><h3class="show-anchors"><div>ENS Name Resolution<divclass="anchors"><aclass="self"href="/v5/migration/ethers-v4/#migration-v4--contracts--ens-name-resolution"></a></div></div></h3><p>The name of the resolved address has changed. If the address passed into the constructor was an ENS name, the address will be resolved before any calls are made to the contract.</p>
<p>The name of the property where the resolved address has changed from <codeclass="inline">addressPromise</code> to <codeclass="inline">resolvedAddress</code>.</p>
</div><aname="migration-v4--contracts--gas-estimation"></a><h3class="show-anchors"><div>Gas Estimation<divclass="anchors"><aclass="self"href="/v5/migration/ethers-v4/#migration-v4--contracts--gas-estimation"></a></div></div></h3><p>The only difference in gas estimation is that the bucket has changed its name from <codeclass="inline">estimate</code> to <codeclass="inline">estimateGas</code>.</p>
</div><aname="migration-v4--contracts--functions"></a><h3class="show-anchors"><div>Functions<divclass="anchors"><aclass="self"href="/v5/migration/ethers-v4/#migration-v4--contracts--functions"></a></div></div></h3><p>In a contract in ethers, there is a <codeclass="inline">functions</code> bucket, which exposes all the methods of a contract.</p>
<p>All these functions are available on the root contract itself as well and historically there was no difference between <codeclass="inline">contact.foo</code> and <codeclass="inline">contract.functions.foo</code>. The original reason for the <codeclass="inline">functions</code> bucket was to help when there were method names that collided with other buckets, which is rare.</p>
<p>In v5, the <codeclass="inline">functions</code> bucket is now intended to help with frameworks and for the new error recovery API, so most users should use the methods on the root contract.</p>
<p>The main difference will occur when a contract method only returns a single item. The root method will dereference this automatically while the <codeclass="inline">functions</code> bucket will preserve it as an <ahref="/v5/api/utils/abi/interface/#Result">Result</a>.</p>
<p>If a method returns multiple items, there is no difference.</p>
<p>This helps when creating a framework, since the result will always be known to have the same number of components as the <ahref="/v5/api/utils/abi/fragments/#Fragment">Fragment</a> outputs, without having to handle the special case of a single return value.</p>
<divclass="code-title"><div>Functions Bucket</div></div><divclass="code">const abi = [
<aname="migration-v4--errors--namespace"></a><h3class="show-anchors"><div>Namespace<divclass="anchors"><aclass="self"href="/v5/migration/ethers-v4/#migration-v4--errors--namespace"></a></div></div></h3><p>All errors now belong to the <ahref="/v5/api/utils/logger/#Logger">Logger</a> class and the related functions have been moved to <ahref="/v5/api/utils/logger/#Logger">Logger</a> instances, which can include a per-package version string.</p>
</div><aname="migration-v4--interface"></a><h2class="show-anchors"><div>Interface<divclass="anchors"><aclass="self"href="/v5/migration/ethers-v4/#migration-v4--interface"></a></div></div></h2><p>The <ahref="/v5/api/utils/abi/interface/">Interface</a> object has undergone the most dramatic changes.</p>
<p>It is no longer a meta-class and now has methods that simplify handling contract interface operations without the need for object inspection and special edge cases.</p>
</div><aname="migration-v4--interface--inspection"></a><h3class="show-anchors"><div>Inspection<divclass="anchors"><aclass="self"href="/v5/migration/ethers-v4/#migration-v4--interface--inspection"></a></div></div></h3><p>Interrogating properties about a function or event can now (mostly) be done directly on the <ahref="/v5/api/utils/abi/fragments/#Fragment">Fragment</a> object.</p>
<aname="migration-v4--wallet--mnemonic-phrases"></a><h3class="show-anchors"><div>Mnemonic Phrases<divclass="anchors"><aclass="self"href="/v5/migration/ethers-v4/#migration-v4--wallet--mnemonic-phrases"></a></div></div></h3><p>The <b>mnemonic</b> phrase and related properties have been merged into a single <codeclass="inline">mnemonic</code> object, which also now includes the <codeclass="inline">locale</code>.</p>
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