Single Liquidity Pool

To store a single liquidity pool, we can use a StorageValue:

#[pallet::storage]
pub type LiquidityPoolBalance<T: Config> = StorageValue<_, Balance, ValueQuery>;

In this example, we define a StorageValue named LiquidityPoolBalance that stores a single Balance value. With database interactions, storage operation return is always an option. There is either Some value at a key or there is None value at a specific key. The default behavior for accessing storage is OptionQuery, which exposes exactly that information back. However, in practice, there are some scenarios where you would like None to actually represent some value. The common example is a Balance where None is exactly the same as having a zero balance. In this case, you would rather have the storage return a 0 rather than an Option each time you query and use the balance. So for convenience, ValueQuery will return a default value for a type rather than having you deal with an optional value. The default value for a None can be modified by using the DefaultValue.

Drawbacks:

• Limited to storing only one liquidity pool
• Cannot handle multiple trading pairs or liquidity pools