UniversalCollection and BasicNFT Contracts

contracts/BasicNFT.cdc

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+/* 
+*
+*  This is an basic implementation of a Flow Non-Fungible Token using the V2 standard.
+*  It shows that a basic NFT can be defined in very few lines of code (less than 100 here)
+*
+*  Unlike the `ExampleNFT-v2` contract, this NFT illustrates a minimal implementation
+*  of an NFT that is now possible with the NFT standard since Events, collections,
+*  and other old requirements are not required any more.
+* 
+*  It also includes minimal metadata to showcase the simplicity
+*   
+*/
+
+import "NonFungibleToken"
+import "MetadataViews"
+import "ViewResolver"
+import "UniversalCollection"
+
+access(all) contract BasicNFT: NonFungibleToken {
+
+    /// The only thing that an NFT really needs to have is this resource definition
+    access(all) resource NFT: NonFungibleToken.NFT {
+        /// Arbitrary trait mapping metadata
+        access(self) let metadata: {String: AnyStruct}
+
+        access(all) let id: UInt64
+
+        init(
+            metadata: {String: AnyStruct},
+        ) {
+            self.id = self.uuid
+            self.metadata = metadata
+        }
+
+        access(all) fun createEmptyCollection(): @{NonFungibleToken.Collection} {
+            return <- BasicNFT.createEmptyCollection(nftType: self.getType())
+        }
+
+        /// Uses the basic NFT views
+        access(all) view fun getViews(): [Type] {
+            return [
+                Type<MetadataViews.Display>(),
+                Type<MetadataViews.Serial>(),
+                Type<MetadataViews.Traits>(),
+                Type<MetadataViews.NFTCollectionData>(),
+                Type<MetadataViews.NFTCollectionDisplay>()
+            ]
+        }
+
+        access(all) fun resolveView(_ view: Type): AnyStruct? {
+            switch view {
+                case Type<MetadataViews.Display>():
+                    return MetadataViews.Display(
+                        name: self.metadata["name"] as! String,
+                        description: self.metadata["description"] as! String,
+                        thumbnail: MetadataViews.HTTPFile(
+                            url: self.metadata["thumbnail"] as! String
+                        )
+                    )
+                case Type<MetadataViews.Serial>():
+                    return MetadataViews.Serial(
+                        self.id
+                    )
+                case Type<MetadataViews.Traits>():
+                    return MetadataViews.dictToTraits(dict: self.metadata, excludedNames: nil)
+                case Type<MetadataViews.NFTCollectionData>():
+                    return BasicNFT.resolveContractView(resourceType: nil, viewType: Type<MetadataViews.NFTCollectionData>())
+                case Type<MetadataViews.NFTCollectionDisplay>():
+                    return BasicNFT.resolveContractView(resourceType: nil, viewType: Type<MetadataViews.NFTCollectionDisplay>())
+            }
+            return nil
+        }
+    }
+
+    access(all) view fun getContractViews(resourceType: Type?): [Type] {
+        return [
+            Type<MetadataViews.NFTCollectionData>(),
+            Type<MetadataViews.NFTCollectionDisplay>()
+        ]
+    }
+
+    access(all) fun resolveContractView(resourceType: Type?, viewType: Type): AnyStruct? {
+        switch viewType {
+            case Type<MetadataViews.NFTCollectionData>():
+                let collectionRef = self.account.storage.borrow<&UniversalCollection.Collection>(
+                        from: /storage/flowBasicNFTCollection
+                    ) ?? panic("Could not borrow a reference to the stored collection")
+                let collectionData = MetadataViews.NFTCollectionData(
+                    storagePath: collectionRef.storagePath,
+                    publicPath: collectionRef.publicPath,
+                    publicCollection: Type<&UniversalCollection.Collection>(),
+                    publicLinkedType: Type<&UniversalCollection.Collection>(),
+                    createEmptyCollectionFunction: (fun(): @{NonFungibleToken.Collection} {
+                        return <-BasicNFT.createEmptyCollection(nftType: Type<@BasicNFT.NFT>())
+                    })
+                )
+                return collectionData
+            case Type<MetadataViews.NFTCollectionDisplay>():
+                let media = MetadataViews.Media(
+                    file: MetadataViews.HTTPFile(
+                        url: "https://assets.website-files.com/5f6294c0c7a8cdd643b1c820/5f6294c0c7a8cda55cb1c936_Flow_Wordmark.svg"
+                    ),
+                    mediaType: "image/svg+xml"
+                )
+                return MetadataViews.NFTCollectionDisplay(
+                    name: "The Example Collection",
+                    description: "This collection is used as an example to help you develop your next Flow NFT.",
+                    externalURL: MetadataViews.ExternalURL("https://example-nft.onflow.org"),
+                    squareImage: media,
+                    bannerImage: media,
+                    socials: {
+                        "twitter": MetadataViews.ExternalURL("https://twitter.com/flow_blockchain")
+                    }
+                )
+        }
+        return nil
+    }
+
+    access(all) resource NFTMinter {
+        access(all) fun mintNFT(metadata: {String: AnyStruct}): @BasicNFT.NFT {
+           return <- create NFT(metadata: metadata)
+        }
+    }
+
+    access(all) fun createEmptyCollection(nftType: Type): @{NonFungibleToken.Collection} {
+        return <- UniversalCollection.createEmptyCollection(identifier: "flowBasicNFTCollection", type: Type<@BasicNFT.NFT>())
+    }
+
+    init() {
+        let minter <- create NFTMinter()
+        self.account.storage.save(<-minter, to: /storage/flowBasicNFTMinterPath)
+
+        let collection <- self.createEmptyCollection(nftType: Type<@BasicNFT.NFT>())
+        self.account.storage.save(<-collection, to: /storage/flowBasicNFTCollection)
+    }
+}
+

contracts/UniversalCollection.cdc

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+/* 
+*
+* This is an example collection that can store any one type of NFT
+* The Collection is restricted to one NFT type.
+* This allows developers to write NFT contracts without having
+* to also write all of the Collection boilerplate code,
+* saving many lines of code.
+*
+*/
+
+import "NonFungibleToken"
+import "MetadataViews"
+import "ViewResolver"
+
+access(all) contract UniversalCollection {
+
+    /// The typical Collection resource, but one that anyone can use
+    ///
+    access(all) resource Collection: NonFungibleToken.Collection {
+
+        /// every Universal collection supports a single type
+        /// All deposits and withdrawals must be of this type
+        access(all) let supportedType : Type
+
+        /// The path identifier
+        access(all) let identifier: String
+
+        /// Dictionary mapping NFT IDs to the stored NFTs
+        access(contract) var ownedNFTs: @{UInt64: {NonFungibleToken.NFT}}
+
+        access(all) var storagePath: StoragePath
+        access(all) var publicPath: PublicPath
+
+        access(all) fun createEmptyCollection(): @{NonFungibleToken.Collection} {
+            return <- create Collection(identifier: self.identifier, type: self.supportedType)
+        }
+
+        init (identifier: String, type:Type) {
+            self.ownedNFTs <- {}
+            self.identifier = identifier
+            self.supportedType = type
+            self.storagePath = StoragePath(identifier: identifier)!
+            self.publicPath = PublicPath(identifier: identifier)!
+        }
+
+        /// getSupportedNFTTypes returns a list of NFT types that this receiver accepts
+        access(all) view fun getSupportedNFTTypes(): {Type: Bool} {
+            let supportedTypes: {Type: Bool} = {}
+            supportedTypes[self.supportedType] = true
+            return supportedTypes
+        }
+
+        /// Returns whether or not the given type is accepted by the collection
+        access(all) view fun isSupportedNFTType(type: Type): Bool {
+            if type == self.supportedType {
+                return true
+            } else {
+                return false
+            }
+        }
+
+        /// withdraw removes an NFT from the collection and moves it to the caller
+        access(NonFungibleToken.Withdraw | NonFungibleToken.Owner) fun withdraw(withdrawID: UInt64): @{NonFungibleToken.NFT} {
+            let token <- self.ownedNFTs.remove(key: withdrawID)
+            ?? panic("Could not withdraw an NFT with the ID: ".concat(withdrawID.toString()).concat(" from the collection"))
+
+            return <-token
+        }
+
+        /// deposit takes a NFT and adds it to the collections dictionary
+        /// and adds the ID to the id array
+        access(all) fun deposit(token: @{NonFungibleToken.NFT}) {
+            if self.supportedType != token.getType() {
+                panic("Cannot deposit an NFT of the given type")
+            }
+
+            // add the new token to the dictionary which removes the old one
+            let oldToken <- self.ownedNFTs[token.id] <- token
+            destroy oldToken
+        }
+
+        /// getIDs returns an array of the IDs that are in the collection
+        access(all) view fun getIDs(): [UInt64] {
+            return self.ownedNFTs.keys
+        }
+
+        /// getLength retusnt the number of items in the collection
+        access(all) view fun getLength(): Int {
+            return self.ownedNFTs.length
+        }
+
+        /// Borrows a reference to an NFT in the collection if it is there
+        /// otherwise, returns `nil`
+        access(all) view fun borrowNFT(_ id: UInt64): &{NonFungibleToken.NFT}? {
+            return (&self.ownedNFTs[id] as &{NonFungibleToken.NFT}?)
+        }
+
+        /// Borrow the view resolver for the specified NFT ID
+        access(all) view fun borrowViewResolver(id: UInt64): &{ViewResolver.Resolver}? {
+            return (&self.ownedNFTs[id] as &{ViewResolver.Resolver}?)!
+        }
+    }
+
+    /// Public function that anyone can call to create
+    /// a new empty collection with the specified type restriction
+    /// NFT contracts can include a call to this method in 
+    /// their own createEmptyCollection method
+    access(all) fun createEmptyCollection(identifier: String, type: Type): @{NonFungibleToken.Collection} {
+        return <- create Collection(identifier: identifier, type:type)
+    }
+}