https://coderrob.com/tags/solidity/Recent content in Solidity on CoderrobHugoen-USWed, 03 Nov 2021 16:46:16 -0500https://coderrob.com/posts/creating-pfp-nft-smart-contracts/Wed, 03 Nov 2021 16:46:16 -0500https://coderrob.com/posts/creating-pfp-nft-smart-contracts/<p>A profile-picture NFT contract has one deceptively simple job: connect each token ID to the correct metadata.</p> <p>The contract in this post does that with a reveal workflow. Before reveal, every minted token returns the same placeholder metadata. After reveal, token <code>42</code> returns the metadata assigned to token <code>42</code>.</p> <div class="highlight"><pre tabindex="0" style="color:#f8f8f2;background-color:#000;-moz-tab-size:4;-o-tab-size:4;tab-size:4;-webkit-text-size-adjust:none;"><code class="language-text" data-lang="text"><span style="display:flex;"><span>before reveal </span></span><span style="display:flex;"><span>token 42 -&gt; ipfs://&lt;placeholder-cid&gt;/placeholder.json </span></span><span style="display:flex;"><span> </span></span><span style="display:flex;"><span>after reveal </span></span><span style="display:flex;"><span>token 42 -&gt; ipfs://&lt;metadata-cid&gt;/42.json </span></span></code></pre></div><p>The useful part is not merely concatenating a number onto a string. We also need to enforce the supply cap, reject nonexistent token IDs, stop minting before disclosure, prove that the final metadata was chosen before deployment, and freeze that metadata after reveal.</p>