Initialization

Storage is declared through the use of the storage keyword.

Inside the storage block each variable is named, associated with a type and a default value.

storage {
    // variable_name1: variable_type1 = default_value1,
    // variable_name2: variable_type2 = default_value2,
    // ...
}

Example

In the following example we will take a look at two ways of storing a struct.

• Explicitly declaring the values in the storage block
• Encapsulating the values in an associated function

We'll begin by defining the Owner & Role data structures and implement a default constructor on the Owner.

struct Owner {
    maximum_owners: u64,
    role: Role,
}

impl Owner {
    // a constructor that can be evaluated to a constant `Owner` during compilation
    fn default() -> Self {
        Self {
            maximum_owners: 10,
            role: Role::FullAccess,
        }
    }
}

enum Role {
    FullAccess: (),
    PartialAcess: (),
    NoAccess: (),
}

Now that we have our data structures we'll keep track of how many current_owners we have and declare the owner in the two aformentioned styles.

storage {
    current_owners: u64 = 0,
    explicit_declaration: Owner = Owner {
        maximum_owners: 10,
        role: Role::FullAccess,
    },
    encapsulated_declaration: Owner = Owner::default(),
}

An explicit declaration is likely to be sufficient for most types. However, it may be preferable to encapsulate the initialization of complex types within a constructor in order to keep the code concise.

Note that the constructors used in storage blocks must evaluate to a constant during compilation.