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Ability: Store

The key ability requires all fields to have store, which defines what the store ability means: it is the ability to serve as a field of an Object. A struct with copy or drop but without store can never be stored. A type with key but without store cannot be wrapped - used as a field—in another object, and is constrained to always remain at the top level.

Definition​

The store ability allows a type to be used as a field in a struct with the key ability.

use std::string::String;

/// Extra metadata with `store`; all fields must have `store` as well!
public struct Metadata has store {
    bio: String,
}

/// An object for a single user record.
public struct User has key {
    id: UID,
    name: String,       // String has `store`
    age: u8,            // All integers have `store`
    metadata: Metadata, // Another type with the `store` ability
}

Relation to copy and drop​

All three non-key abilities can be used in any combination.

Relation to key​

An object with the store ability can be stored in other objects.

While not a language or verifier feature, store acts as a public modifier on a struct, allowing calling public transfer functions which do not have an internal constraint.

Types with the store Ability​

All native types (except references) in Move have the store ability. This includes:

All of the types defined in the standard library have the store ability as well. This includes:

Further Reading​