Ethereum Cookbook

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All the contracts we have created so far only stores and manages the token ID. A token will have a lot more data depending on the use case. One quick way to store the details is by using a string of characters designed for unambiguous identification. The Uniform Resource Identifier (URI) scheme is one such implementation that uses the type string:

mapping(uint256 => string) internal tokenURIs;

This allows any data to be stored as a token. Read and write is performed with the help of dedicated functions:

/** * @dev Returns an URI for a given token ID * @dev Throws if the token ID does not exist. May return an empty string. * @param _tokenId uint256 ID of the token to query */function tokenURI(uint256 _tokenId) public view returns ...