Vara Fungible Token (VFT)

The Vara Fungible Token Standard provides a unified API for programs to implement token functionalities. It encompasses critical operations like token transfer and approvals for third-party spending on the blockchain. Below is a detailed look at the state of the program, its interface, and key methods to facilitate these operations.

Functions

Approve(spender, value)
Transfer(to, value)
TransferFrom(from, to, value)
Allowance(owner, spender)
BalanceOf(owner)
Decimals()
Name()
Symbol()
TotalSupply()

Events

Approval(owner, spender, value);
Transfer(from, to, value);

Key methods

Approve

pub fn approve(&mut self, spender: ActorId, value: U256) -> bool

This function allows a designated spender (spender) to withdraw up to an value of tokens from your account, multiple times up to the amount limit. Resets allowance to value with a subsequent call. Returns a boolean value indicating whether the operation succeeded.

Upon successful execution, triggers the event:

Approval {
    owner: ActorId,
    spender: ActorId,
    value: U256,
}

Transfer

pub fn transfer(&mut self, to: ActorId, value: U256) -> bool

Transfers the specified value of tokens to the account to. Returns a boolean value indicating whether the operation

Upon successful execution, triggers the event:

Transfer {
    from: ActorId,
    to: ActorId,
    value: U256,
}

TransferFrom

pub fn transfer_from(&mut self, from: ActorId, to: ActorId, value: U256) -> bool

Transfers a specified value of tokens from one account to another, using the allowance mechanism. Value is then deducted from the caller’s allowance. Returns a boolean value indicating whether the operation succeeded.

Upon successful execution, triggers the event:

Transfer {
    from: ActorId,
    to: ActorId,
    value: U256,
}

Query methods

name

Returns the name of the token.

pub fn name(&self) -> String 

symbol

Returns the symbol of the token.

pub fn symbol(&self) -> String 

decimals

Returns the decimals of the token.

pub fn decimals(&self) -> u8

total_supply

Returns the total supply of the token.

pub fn total_supply(&self) -> U256

balance_of

Returns the token balance of the owner address.

pub fn balance_of(&self, account: ActorId) -> U256

allowance

Returns the number of tokens the spender account is authorized to spend on behalf of the owner.

pub fn allowance(&self, owner: ActorId, spender: ActorId) -> U256 

Conclusion

The provided service is a foundational base for creating your own token, rather than a complete application. It can be extended and inherited to add additional functionality, allowing developers to build upon this framework. The code for this service is available on GitHub.

By adhering to this standard, programs ensure interoperability and a consistent user experience across platforms and applications within the blockchain ecosystem. dApp developers can also ensure that their in-app tokens, built on this standard, will be natively displayed in user wallets without additional integration efforts, as long as wallet applications support this standard.