How to use different argument types across different pallets

Question

I am trying to use one pallet function inside my own pallet... but the argument types have problems...

  #[pallet::config]
    pub trait Config: frame_system::Config + pallet_vesting::Config {
    ...}
  #[pallet::call]
  impl<T: Config> Pallet<T> {
    ...
    pub fn vested_transfer(
        origin: OriginFor<T>,
        target: <T::Lookup as StaticLookup>::Source,
        locked: BalanceOf<T>,
        per_block: BalanceOf<T>,
        starting_block: BlockNumberFor<T>,
    ) -> DispatchResultWithPostInfo {
        let vesting_info = pallet_vesting::VestingInfo::<BalanceOf<T>, BlockNumberFor<T>>::new(
            locked,
            per_block,
            starting_block,
        );
        let is_valid = vesting_info.is_valid();
        ensure!(is_valid, "invalid vesting_info");
        let res = pallet_vesting::Pallet::<T>::vested_transfer(origin, target, vesting_info);

Then the error message for the 3rd argument vesting_info: ... vesting_info... expected pallet_vesting::Config::Currency, found pallet::Config::Currency

Then I tried this to cast the vesting_info type:

vesting_info as pallet_vesting::Config::Currency

... error message: use fully-qualified syntax: <Type as pallet_vesting::Config>::Currency

Then I tried this to fix that the 3rd argument:

vesting_info as <<T as pallet::Config>::Currency as pallet_vesting::Config>::Currency,

... error message: use of undeclared crate or module pallet

Then I tried this to fix that the 3rd argument:

vesting_info as <<T as Config>::Currency as pallet_vesting::Config>::Currency,

... error message: the trait pallet_vesting::Config is not implemented for <T as pallet::Config>::Currency... an as expression can only be used to convert between primitive types or to coerce to a specific trait object

Then I tried this to fix that the 3rd argument:

vesting_info as <<T as Self::Config>::Currency as pallet_vesting::Config>::Currency,

... error message: the name Config is defined multiple times; cannot find associated type Currency in Self::Config

how to use "pallet" or different pallet function argument types ?

Answer 1

The quick and easy way to solve your issue would be to tightly couple your pallet's Config trait with the one of pallet_vesting. This way, you would not have to define the Currency trait in your Config.

type BalanceOf<T> = <<T as pallet_vesting::Config>::Currency as Currency<
        <T as frame_system::Config>::AccountId,
    >>::Balance;

pub trait Config: frame_system::Config + pallet_vesting::Config {
   // your custom associated types
}

Then you can simply call the vested_transfer like so

#[pallet::weight(10_000)]
pub fn your_custom_extrinsic(
    origin: OriginFor<T>,
    target: <T::Lookup as sp_runtime::traits::StaticLookup>::Source,
    vesting_amount: BalanceOf<T>,
    per_block: BalanceOf<T>,
    lock_period: T::BlockNumber,
) -> DispatchResult {
    let vesting_info = pallet_vesting::VestingInfo::<BalanceOf<T>, T::BlockNumber>::new(
        vesting_amount,
        per_block,
        lock_period,
    );
    pallet_vesting::Pallet::<T>::vested_transfer(origin, target, vesting_info)
}

Without tight coupling, it is more complicated. On a high level, you would need to provide a conversion from your pallet::Config::Currency trait to the one of pallet_vesting::Config::Currency.