Missing trait problem

Question

Hello the following code snippet is giving me headaches:

mod items;
pub use super::*;
pub use crate::roles::items::*;
pub type BalanceOf<T> = <<T as pallet::Config>::Currency as Currency<<T as frame_system::Config>::AccountId>>::Balance;
pub type AccountIdOf<T> = <T as frame_system::Config>::AccountId;
pub type Contributors<T> = Vec<AccountIdOf<T>>;
pub type HouseIndex = u32;
pub type Bool = bool;



#[derive(Debug, PartialEq, Encode, Decode)]
pub struct Investor<T,U>{
    pub account_id:T,
    pub nft:U,
}
impl<T,U> Investor<T,U>{
    pub fn new(acc: T,nft:U)-> Self{
        Investor{
            account_id: acc,
            nft: nft,
        }        
    }

}

impl<T:pallet::Config+frame_system::Config,U> Investor<T,U>{
    
    pub fn contribute(origin:OriginFor<T>,acc:AccountIdOf<T> ,value:BalanceOf<T>) -> DispatchResult{
        let c1=Contribution::new(&acc,&value);
        let _who = ensure_signed(origin)?;
        let _now = <frame_system::Pallet<T>>::block_number();
        if ContributionsLog::<T>::contains_key(c1.account){
            ContributionsLog::<T>::mutate(c1.account, |val|{
                *val += *c1.amount;
            })
        } else {
            ContributionsLog::<T>::insert(&acc,value);
            ContAccounts::<T>::mutate(|val|{
                val.push(acc);
            })
        }
        
        //function taking contribution storage and amount as inputs here
        Ok(().into())


    }
}

this code is located in a mod.rs file it looks good to me, until I try to use the contribute method in my lib.rs:

impl<T: Config> Pallet<T> {
  
  #[pallet::weight(10_000 + T::DbWeight::get().writes(1))]
  pub fn do_something(origin: OriginFor<T>, something: u32, acc:AccountIdOf<T> ,rent:BalanceOf<T>,cd:CID,prop:Properties,start:Option<BlockNumberOf<T>>,end:Option<BlockNumberOf<T>>) -> DispatchResult 
  { 
     let who = ensure_signed(origin)?;
     let dev=Investor::new(&acc,something);
     Investor::<T::AccountId,u32>::contribute(who,dev.account_id,rent);
    
     <Something<T>>::put(dev.nft+something);

     Self::deposit_event(Event::SomethingStored(something, who));
     Ok(())
  }

this then give me the following error:

error[E0599]: the function or associated item `contribute` exists for struct `roles::Investor<<T as frame_system::Config>::AccountId, u32>`, but its trait bounds were not satisfied
   --> pallets/template/src/lib.rs:144:40
    |
144 |          Investor::<T::AccountId,u32>::contribute(who,dev.account_id,rent);
    |                                        ^^^^^^^^^^ function or associated item cannot be called on `roles::Investor<<T as frame_system::Config>::AccountId, u32>` due to unsatisfied trait bounds
    |
   ::: pallets/template/src/roles/mod.rs:14:1
    |
14  | pub struct Investor<T,U>{
    | ------------------------ function or associated item `contribute` not found for this
    |
    = note: the following trait bounds were not satisfied:
            `<T as frame_system::Config>::AccountId: pallet::Config`
            `<T as frame_system::Config>::AccountId: frame_system::Config`

trying to implement investor as below didn't solve the problem either:

    impl<T:frame_system::Config+pallet::Config,U> Investor<T,U>{
    pub fn new(acc: T,nft:U)-> Self{
        Investor{
            account_id: acc,
            nft: nft,
        }        
    }

  }

Any advice? Please?

link to the repo/lib.rs: https://github.com/Fair-Squares/fair-squares/blob/structure_template/pallets/template/src/lib.rs Kazu

Answer 1

You are really mixing up what the generic types mean to you.

In one case, you have T represent the AccountId directly, and in the other case you have it represent your Config.

Here is a minimal sample which uses most of the same code as what you want and compiles:

#![cfg_attr(not(feature = "std"), no_std)]

pub use pallet::*;

#[frame_support::pallet]
pub mod pallet {
    use frame_support::{pallet_prelude::*, traits::Currency};
    use frame_system::pallet_prelude::*;

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

    #[pallet::config]
    pub trait Config: frame_system::Config {
        type Currency: Currency<Self::AccountId>;
    }

    #[pallet::pallet]
    #[pallet::generate_store(pub(super) trait Store)]
    pub struct Pallet<T>(_);

    #[pallet::call]
    impl<T: Config> Pallet<T> {
        #[pallet::weight(10_000 + T::DbWeight::get().writes(1))]
        pub fn do_something(
            origin: OriginFor<T>,
            something: u32,
            acc: AccountIdOf<T>,
            rent: BalanceOf<T>,
        ) -> DispatchResult {
            let who = ensure_signed(origin.clone())?;
            let dev = Investor::<T, u32>::new(acc, something);
            Investor::<T, u32>::contribute(origin, dev.account_id, rent)?;

            // Do something

            Ok(())
        }
    }

    #[derive(Debug, PartialEq, Encode, Decode)]
    pub struct Investor<T: Config, U> {
        pub account_id: AccountIdOf<T>,
        pub nft: U,
    }

    impl<T: Config, U> Investor<T, U> {
        pub fn new(acc: AccountIdOf<T>, nft: U) -> Self {
            Investor { account_id: acc, nft }
        }

        pub fn contribute(
            origin: OriginFor<T>,
            acc: AccountIdOf<T>,
            value: BalanceOf<T>,
        ) -> DispatchResult {
            // Do something

            Ok(())
        }
    }
}

Note in this case, T always represents T: Config, and AccountId is always called with AccountIdOf<T>.

Answer 2

Rewrite your struct so that it's not generic over T:

For example:

#[derive(Debug, PartialEq, Encode, Decode)]
pub struct Investor<AccountId, U>{
    pub account_id: AccountId,
    pub nft: U,
}

and then apply the changes to the other parts of your code.

Answer 3

To create a runtime you need to call construct_runtime! macro that will create your pallet type, but you also have to configure the pallets so in this case you will need a pub trait Config: frame_system::Config {pub trait Config: frame_system::Config {, have a look at how the nicks pallet is done for example:

https://docs.substrate.io/tutorials/v3/add-a-pallet/