fn decrease_allowance(&mut self, spender: AccountId, delta_value: Balance) {
        let owner = Self::env().caller();
        let allowance = self.allowance(owner, spender);
        assert!(allowance >= delta_value, "{}", Erc20Error::InsufficientAllowance.as_ref());

        self._approve_from_to(owner, spender, allowance - delta_value)
    }
/// Atomically decreases the allowance granted to `spender` by the caller.
///
/// An `Approval` event is emitted.
///
/// # Errors
///
/// Panics `InsufficientAllowance` error if there are not enough tokens allowed
/// by owner for `spender`.
///
/// Panics `ZeroSenderAddress` error if sender's address is zero.
///
/// Panics `ZeroRecipientAddress` error if recipient's address is zero.
Atomically decreases the allowance granted to `spender` by the caller.
An `Approval` event is emitted.
Atomically decreases the allowance granted to ` spender ` by the caller . An ` Approval ` event is emitted .
fn decrease_allowance(&mut self, spender: AccountId, delta_value: Balance) {
        let owner = Self::env().caller();
        let allowance = self.allowance(owner, spender);
        assert!(allowance >= delta_value, "{}", Erc20Error::InsufficientAllowance.as_ref());
        self._approve_from_to(owner, spender, allowance - delta_value)
    }
fn decrease_allowance ( & mut self , spender : AccountId , delta_value : Balance ) { let owner = Self :: env ( ) . caller ( ) ; let allowance = self . allowance ( owner , spender ) ; assert ! ( allowance delta_value " " Erc20Error InsufficientAllowance as_ref ( ) ) ; self . _approve_from_to ( owner , spender , allowance - delta_value ) }
Atomically decreases the allowance granted to `spender` by the caller.
Atomically decreases the allowance granted to ` spender ` by the caller .
&mut self
spender
AccountId
delta_value
Balance
&mut self
spender
AccountId
delta_value
Balance
errors
Panics `InsufficientAllowance` error if there are not enough tokens allowed
by owner for `spender`.

Panics `ZeroSenderAddress` error if sender's address is zero.

Panics `ZeroRecipientAddress` error if recipient's address is zero.
Panics ` InsufficientAllowance ` error if there are not enough tokens allowed by owner for ` spender ` . Panics ` ZeroSenderAddress ` error if sender ' s address is zero . Panics ` ZeroRecipientAddress ` error if recipient ' s address is zero .