| status | flip | authors | sponsor | updated |
|---|---|---|---|---|
Implemented |
1087 |
Álvaro Lillo Igualada ([email protected]) |
Josh Hannan ([email protected]) |
2022-08-16 |
The goal of this proposal is to allow Fungible Tokens (FT) to provide metadata, in a similar fashion as the NFT Metadata Standard, FLIP 636. This will allow better interoperability between fungible tokens and external applications.
As the Flow ecosystem continues to grow, the need of assuring contract and external apps interoperability increases. The development of the NFT Metadata standard showed how important it is for NFTs on Flow to be able to communicate their features to other dapps, and the advantages of doing so in a standardized way.
The creation of a Metadata standard for fungible tokens will bring two major user benefits: discoverability and interoperability. It will make it easier for any FT to be presented in any app that displays fungible tokens, and will also allow those FTs to communicate how they can be used programmatically.
The core of this proposal is to add the following interface and have any FungibleToken.Vault implement it. This is the same interface that can be found in the NFT metadata contract.
/// Provides access to a set of metadata views. A struct or
/// resource (e.g. a Vault) can implement this interface to provide access to
/// the views that it supports.
///
pub resource interface Resolver {
pub fun getViews(): [Type]
pub fun resolveView(_ view: Type): AnyStruct?
}Also, based on the experience gained from the NFT metadata standard, implementations are required to provide an FTView view, which provides a full picture of the FT. It wraps the FTDisplay and FTVaultData views.
/// FTView wraps FTDisplay and FTVaultData, and is used
/// to give a complete picture of a FT. Most FTs should implement this
/// view.
///
pub struct FTView {
pub let ftDisplay: FTDisplay?
pub let vaultData: FTVaultData?
init(
ftDisplay: FTDisplay?,
vaultData: FTVaultData?
) {
self.ftDisplay = ftDisplay
self.vaultData = vaultData
}
}The FTView contains two sub-views:
FTDisplay, which provides the "human readable" information about the fungible token; andFTVaultData, which provides the data needed to interact with the fungible token (paths, types linked to those paths, similar toNFTCollectionData)
/// View to expose the information needed to showcase this FT.
/// This can be used by applications to give an overview and
/// graphics of the FT.
///
pub struct FTDisplay {
/// Name that should be used when displaying this FT.
pub let name: String
/// Description that should be used to give an overview of this FT.
pub let description: String?
/// A small logo that represents the FT.
///
/// This field should be a web-friendly file (i.e JPEG, PNG)
/// that can be displayed in lists, link previews, etc.
pub let logo: AnyStruct{File}?
/// External link to a URL to view more information about this token.
pub let externalURL: ExternalURL?
/// Social links to reach this token's social homepages.
/// Possible keys may be "instagram", "twitter", "discord", etc.
pub let socials: {String: ExternalURL}?
init(
name: String,
description: String?,
logo: AnyStruct{File}?,
externalURL: ExternalURL?,
socials: {String: ExternalURL}?
) {
self.name = name
self.description = description
self.logo = logo
self.externalURL = externalURL
self.socials = socials
}
} /// View to expose the information needed store and interact with a FT vault.
/// This can be used by applications to setup a FT vault with proper
/// storage and public capabilities.
///
pub struct FTVaultData {
/// Path in storage where this FT vault is recommended to be stored.
pub let storagePath: StoragePath
/// Public path which must be linked to expose public capabilities of
/// this FT, including standard FT interfaces and metadataviews
/// interfaces
pub let publicPath: PublicPath
/// Private path which should be linked to expose the provider
/// capability to withdraw funds from the vault
pub let providerPath: PrivatePath
/// Type that should be linked at the aforementioned public path. This
/// is normally a restricted type with many interfaces. Notably the
/// `FT.Balance`, `FT.Receiver`, and `FungibleMetadataViews.Resolver`
/// interfaces are required.
pub let publicLinkedType: Type
/// Type that should be linked at the aforementioned private path. This
/// is normally a restricted type with at a minimum the `FT.Provider`
/// interface
pub let providerLinkedType: Type
/// Function that allows creation of an empty FT vault that is intended
/// to store the funds.
pub let createEmptyVault: ((): @FungibleToken.Vault)
init(
storagePath: StoragePath,
publicPath: PublicPath,
providerPath: PrivatePath,
publicCollection: Type,
publicLinkedType: Type,
providerLinkedType: Type,
createEmptyVaultFunction: ((): @FungibleToken.Vault)
) {
pre {
publicLinkedType.isSubtype(of: Type<&{FungibleToken.Receiver, FungibleToken.Balance, Resolver}>()): "Public type must include FungibleToken.Receiver, FungibleToken.Balance and FungibleMetadataViews.Resolver interfaces."
providerLinkedType.isSubtype(of: Type<&{FungibleToken.Provider, Resolver}>()): "Provider type must include NonFungibleToken.Provider and FungibleMetadataViews.Resolver interface."
}
self.storagePath = storagePath
self.publicPath = publicPath
self.providerPath = providerPath
self.publicLinkedType = publicLinkedType
self.providerLinkedType = providerLinkedType
self.createEmptyVault = createEmptyVaultFunction
}
}In order to be able to use the FTDisplay we will need to use or import (depending on if this ends up being part of the original MetadataViews.cdc contract or having its own contract) the following views: ExternalURL, File, HTTPFile, IPFSFile, Media and Medias.
Since the MetadataViews contract has been a successful solution for increasing NFT interoperability, no alternatives have been considered.
Due to the potentially dynamic nature of this proposal, the methods that return metadata views can be implemented in any way that the author sees fit which could lead to some non-performant implementations.
This proposal builds on the existing FT interface.
Adhering to this standard will require contract authors to implement a few new methods as part of their FT. They will also likely need to import standard types into their contracts.
There may also need to be a committee, process, and code repository put in place for managing the standard metadata types.
Fungible Token issuers should implement the FTView to achieve the as much ecosystem compatibility as possible.
Guidelines on how to implement the new views will be added to the ExampleToken.cdc contract, and their used will be documented on the flow-ft repo docs.
Fungible Token contract owners will need to update them to add implementations for the new methods.
This feature can be rolled out with no fear of changes to the user. However documentation should be provided on how they can change their contracts and add views.
The existing NFT Metadata views standard has been used as the main inspiration for this proposal.
We should agree on which views, new ones and existing ones, should be needed to implement by any Fungible Token adopting the standard.