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Kento Tomisawa
Kento Tomisawa

Reputation: 13

What does Something get(fn something): Option<u32>; mean in Rust?

I cloned this template. There is a code like this:

decl_storage! {
    trait Store for Module<T: Trait> as TemplateModule {
        Something get(fn something): Option<u32>;
    }
}

What does Something get(fn something): Option<u32>; mean? Especially what is Something before get(fn something)?

Upvotes: 1

Views: 226

Answers (1)

phimuemue
phimuemue

Reputation: 35993

Apparently this macro accepts custom syntax, as documented in https://substrate.dev/rustdocs/v2.0.0-rc5/frame_support/macro.decl_storage.html:

Basic storage can be extended as such:

#vis #name get(fn #getter) config(#field_name) build(#closure): #type = #default;

  • #vis: Set the visibility of the structure. pub or nothing.
  • #name: Name of the storage item, used as a prefix in storage.
  • [optional] get(fn #getter): Implements the function #getter to Module.
  • [optional] config(#field_name): field_name is optional if get is set. Will include the item in GenesisConfig.
  • [optional] build(#closure): Closure called with storage overlays.
  • #type: Storage type.
  • [optional] #default: Value returned when none.

So in your Something is the name of the storage item, used as a prefix in storage.

Upvotes: 1

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