Struct exonum_merkledb::Lazy

pub struct Lazy<T, I> { /* fields omitted */ }

Lazily initialized object in the database.

Unlike eagerly initialized objects, lazy ones are not accessed until a get() method is called; thus, construction of a lazy object is cheap. This can be used to improve performance of a database object, some components of which are rarely accessed.

Note that Groups are already lazy, so it does not make sense to wrap a one into Lazy<_> (although this is technically possible).

Examples

let db = TemporaryDB::new();
let fork = db.fork();
{
    let lazy: Lazy<_, ListIndex<_, String>> =
        Lazy::from_access(&fork, "lazy_list".into()).unwrap();
    lazy.get().push("!".to_owned());
    assert_eq!(lazy.get().len(), 1);
}
// List can then be accessed eagerly.
assert_eq!(
    fork.get_list::<_, String>("lazy_list").get(0),
    Some("!".to_owned())
);

Methods

impl<T, I> Lazy<T, I> where
    T: Access,
    I: FromAccess<T>, 

pub fn get(&self) -> I

Gets the object from the database.

Panics

Panics if the object cannot be restored.

pub fn try_get(&self) -> Result<I, AccessError>

Tries to restore the object from the database.

Trait Implementations

impl<T: Debug, I: Debug> Debug for Lazy<T, I>

fn fmt(&self, f: &mut Formatter) -> Result

Formats the value using the given formatter.

impl<T, I> FromAccess<T> for Lazy<T, I> where
    T: Access,
    I: FromAccess<T>, 

fn from_access(access: T, addr: IndexAddress) -> Result<Self, AccessError>

Constructs the object at the given address.

fn from_root(access: T) -> Result<Self, AccessError>

Constructs the object from the root of the access.