Web3 & DApp Development Fundamentals · Pelajaran

Marketplace

Pencatatan dan transfer

Marketplace adalah pelajaran Web3 & DApp Development Fundamentals gratis di CoddyKit. Ini adalah pelajaran 4 dari 4. Kamu bisa membaca pelajaran lengkapnya di bawah secara gratis — lalu praktikkan langsung di browser dengan editor kode bawaan dan tutor AI 24/7. Ini adalah bagian dari jalur belajar Web3 & DApp Development Fundamentals, dan progresmu tersinkronisasi di web dan aplikasi CoddyKit. Kursus Web3 & DApp Development Fundamentals mencakup 4 pelajaran total.

Bagian dari pelajaran ini belum diterjemahkan dan ditampilkan dalam bahasa Inggris.

How NFT Marketplaces Work

An NFT marketplace lets users list tokens for sale and lets buyers purchase them. Behind the scenes it relies on the ERC-721 approval and transfer mechanics you have already learned.

The marketplace contract never owns your NFT - it just moves it when a sale executes.

The Approval Step

Before listing, the seller must approve the marketplace to move the token. Sellers usually call setApprovalForAll so one approval covers all their NFTs in a collection.

<code>// seller authorizes the marketplace
nft.setApprovalForAll(marketplaceAddress, true);</code>

Storing a Listing

The marketplace records each listing with the seller, the NFT contract, the token id, and the price.

<code>struct Listing {
    address seller;
    address nft;
    uint256 tokenId;
    uint256 price;
}
mapping(bytes32 => Listing) public listings;</code>

Creating a Listing

To list, the seller calls a function that verifies they own the token and that the marketplace is approved, then stores the listing.

<code>function list(address nft, uint256 tokenId, uint256 price) public {
    require(IERC721(nft).ownerOf(tokenId) == msg.sender, 'not owner');
    require(IERC721(nft).isApprovedForAll(msg.sender, address(this)), 'not approved');
    bytes32 id = keccak256(abi.encodePacked(nft, tokenId));
    listings[id] = Listing(msg.sender, nft, tokenId, price);
}</code>

Buying an NFT

A buyer sends the price as Ether. The marketplace transfers the NFT from seller to buyer using safeTransferFrom and forwards the payment.

<code>function buy(bytes32 id) public payable {
    Listing memory l = listings[id];
    require(msg.value >= l.price, 'insufficient payment');
    delete listings[id];
    IERC721(l.nft).safeTransferFrom(l.seller, msg.sender, l.tokenId);
    payable(l.seller).transfer(l.price);
}</code>

Delete Before Transfer

Notice the listing is deleted before external calls. This follows the checks-effects-interactions pattern and prevents reentrancy from buying the same NFT twice.

<code>delete listings[id]; // effect first
// then interactions (transfers)</code>

Marketplace Fees

Marketplaces typically take a percentage fee. The contract splits the payment between the seller and a fee recipient.

<code>uint256 public feeBps = 250; // 2.5%

uint256 fee = (l.price * feeBps) / 10000;
payable(feeRecipient).transfer(fee);
payable(l.seller).transfer(l.price - fee);</code>

Royalties (ERC-2981)

The ERC-2981 standard lets creators earn a royalty on secondary sales. A marketplace queries royaltyInfo and pays the creator their share.

<code>function royaltyInfo(uint256 tokenId, uint256 salePrice)
    external view returns (address receiver, uint256 royaltyAmount);</code>

Cancelling a Listing

Sellers should be able to remove their listing. Only the original seller may cancel.

<code>function cancel(bytes32 id) public {
    require(listings[id].seller == msg.sender, 'not seller');
    delete listings[id];
}</code>

Off-Chain Order Books

Large marketplaces like OpenSea avoid storing every listing on-chain. Instead sellers sign orders off-chain, and the contract only runs the transfer when a buyer submits a matching signed order. This saves enormous gas.

Security Considerations

Marketplaces are high-value targets. Guard against reentrancy, validate ownership and approvals at execution time, and never trust prices or addresses from untrusted input without checks.

Quick Check

Test your understanding of NFT marketplaces.

Recap

You learned how NFT marketplaces operate:

Sellers approve the marketplace, which then transfers on sale (no escrow needed)
Listings store seller, NFT, tokenId, and price
Buying transfers the NFT and forwards payment, deleting the listing first (checks-effects-interactions)
Fees and ERC-2981 royalties split the proceeds
Big marketplaces use off-chain signed orders to save gas

Pertanyaan yang Sering Diajukan

Apakah pelajaran “Marketplace” gratis?

Ya — teks lengkap “Marketplace” gratis dibaca di sini di web. Untuk praktiknya secara interaktif (editor kode bawaan dan tutor AI 24/7) dan buka sisa kursus Web3 & DApp Development Fundamentals, upgrade ke CoddyKit PRO. Kursus Web3 & DApp Development Fundamentals mencakup 4 pelajaran total.

Apa yang akan aku pelajari di “Marketplace”?

Pencatatan dan transfer Kamu berlatih Web3 & DApp Development Fundamentals dengan kode praktik yang langsung kamu jalankan di browser, dan tutor AI 24/7 menjawab pertanyaanmu saat kamu mengerjakan pelajaran ini.

Apakah aku perlu pengalaman untuk memulai Web3 & DApp Development Fundamentals?

Tidak diperlukan pengalaman sebelumnya. Web3 & DApp Development Fundamentals di CoddyKit dirancang untuk pemula hingga pelajar tingkat lanjut, jadi kamu bisa memulai di sini atau dari awal dan belajar sesuai kecepatan kamu sendiri. Ini adalah pelajaran 4 dari 4.

Berapa lama pelajaran “Marketplace” memakan waktu?

Sebagian besar pelajaran CoddyKit memakan waktu sekitar 5–10 menit. Setiap pelajaran ringkas dan interaktif, jadi kamu membuat kemajuan stabil dan melanjutkan dari tempat kamu tinggalkan di web dan aplikasi.

Bisakah aku menulis dan menjalankan kode dalam pelajaran Web3 & DApp Development Fundamentals ini?

Ya. Setiap pelajaran Web3 & DApp Development Fundamentals menyertakan editor kode bawaan, jadi kamu menulis dan menjalankan kode nyata langsung di browser dan mendapatkan umpan balik AI instan — tidak diperlukan penyiapan lokal.

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