iter storage in substrate

Question

I Wanna to create a StoreBasket in Substrate .

I Have Two Struct one for BusinessItem .

#[derive(Clone, Encode, Decode, PartialEq, RuntimeDebug, TypeInfo)]
#[scale_info(skip_type_params(T))]
#[codec(mel_bound())]
pub struct BusinessItem {
    media: Vec<u8>,
    title: Vec<u8>,
    description: Vec<u8>,
    price: u32,
    count: u32,
    itemId: [u8; 16],
}

also i Defined Storage For Item:

#[pallet::storage]
#[pallet::getter(fn items)]
pub(super) type Items<T: Config> = StorageMap<_, Twox64Concat, T::AccountId, Vec<BusinessItem>>;

I wanna to find item in item Storage with itemid , for exmaple i have itemId : X0o788dfgg and i need to find item with this id in storage .

i wrote this code bit it dose not work :

let _itemInfo: Option<&BusinessItem> = items.iter().find(|item| item.itemId == item_id);

whats the problem ? how can i solve this problem ?

Answer 1

---

IterableStorageMap doc.

if let Some(item) = <Items<T>>::iter().find(|(_, i)| i.id == id) {
  log::info!("got {:#?}", item);
}

But I don't recommend using this. Because it will do a lot of r/w, which costs a lot of resources.

Maybe you should add another map to record the mapping ItemId -> AccountId. Or something like that.

---

Okay, I found you are trying to store a Vec<Item> under each AccountId key. I have to say, this has a really bad performance.

let mut matched_items = Vec::new();
<Items<T>>::iter().for_each(|(_, items)| {
  items.iter().for_each(|i| {
    if i.id == id {
      matched_items.push(i.clone());
    }
  })
});