syntax - 什么东西会得到(fn something): Option; mean in Rust?

Question

我克隆了this template。
有这样的代码:

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

Something get(fn something): Option<u32>;是什么意思？
特别是 Something之前的 get(fn something)是什么？

Answer 1

显然，此宏接受https://substrate.dev/rustdocs/v2.0.0-rc5/frame_support/macro.decl_storage.html中记录的自定义语法:

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.

因此，在 Something中是存储项的名称，用作存储中的前缀。