[Bad Example] Process up to a maximum number of elements

[shawntabrizi]

https://libro.blockdeep.dev/critical/Avoid_Unbounded_Iteration.html

The example here isn't that great:

const MAX_ITEMS: usize = 20;

#[pallet::storage]
pub type UnboundedData<T: Config> = StorageValue<_, Vec<u32>;

let big_data = UnboundedData::<T>::get();
for item in big_data.iter().take(MAX_ITEMS) {
    // Process a limited number of items safely
}

In this example, you are reading an unbounded storage item which itself is bad practice.

The better example here would perhaps be an imput to the extrinsic from the user, which is a Vec, and ensuring the length of the vec is within some limit.

[moliholy]

The better example here would perhaps be an imput to the extrinsic from the user, which is a Vec, and ensuring the length of the vec is within some limit.

For that I'd directly recommend to use a BoundedVec in the input itself 🤔

[moliholy]

In this example, you are reading an unbounded storage item which itself is bad practice.

If so, the mere existence of unbounded storage items would be a bad practice. If reading an unbounded storage item is a bad practice, why are unbounded storage items allowed to be declared in the first place?

[shawntabrizi]

They aren't. We don't allow you to make a storage item unbounded unless you put special flags on it.

For that I'd directly recommend to use a BoundedVec in the input itself 🤔

True, but at least the example makes more sense.

The other option where "unbounded iteration" occurs is the rare care you iterate over a storage map, so you can use that example instead.

[moliholy]

The other option where "unbounded iteration" occurs is the rare care you iterate over a storage map, so you can use that example instead.

Yes, that's what I think it best. I'll open a PR soon.

Again, many thanks for your contributions 🙏 .