Struct near_sdk::collections::LazyOption

pub struct LazyOption<T> { /* private fields */ }

An persistent lazy option, that stores a value in the storage.

Implementations

impl<T> LazyOption<T>

pub fn is_some(&self) -> bool

Returns true if the value is present in the storage.

pub fn is_none(&self) -> bool

Returns true if the value is not present in the storage.

impl<T> LazyOption<T>where
    T: BorshSerialize + BorshDeserialize,

pub fn new<S>(storage_key: S, value: Option<&T>) -> Selfwhere
    S: IntoStorageKey,

Create a new lazy option with the given storage_key and the initial value.

Examples

use near_sdk::collections::LazyOption;

let option: LazyOption<u32> = LazyOption::new(b"l", Some(&42));
let another_option: LazyOption<u32> = LazyOption::new(b"l", None);

pub fn remove(&mut self) -> bool

Removes the value from storage without reading it. Returns whether the value was present.

Examples

use near_sdk::collections::LazyOption;

let mut option: LazyOption<u32> = LazyOption::new(b"l", Some(&42));
assert_eq!(option.remove(), true);
assert!(option.is_none());
assert_eq!(option.remove(), false);

pub fn take(&mut self) -> Option<T>

Removes the value from storage and returns it as an option.

Examples

use near_sdk::collections::LazyOption;

let mut option: LazyOption<u32> = LazyOption::new(b"l", Some(&42));
assert_eq!(option.take(), Some(42));
assert!(option.is_none());
assert_eq!(option.take(), None);

pub fn get(&self) -> Option<T>

Gets the value from storage and returns it as an option.

Examples

use near_sdk::collections::LazyOption;

let mut option: LazyOption<u32> = LazyOption::new(b"l", None);
assert_eq!(option.get(), None);
option.set(&42);
assert_eq!(option.get(), Some(42));
assert!(option.is_some());

pub fn set(&mut self, value: &T) -> bool

Sets the value into the storage without reading the previous value and returns whether the previous value was present.

Examples

use near_sdk::collections::LazyOption;

let mut option: LazyOption<u32> = LazyOption::new(b"l", None);
assert_eq!(option.set(&42), false);
assert_eq!(option.set(&420), true);

pub fn replace(&mut self, value: &T) -> Option<T>

Replaces the value in the storage and returns the previous value as an option.

Examples

use near_sdk::collections::LazyOption;

let mut option: LazyOption<u32> = LazyOption::new(b"l", None);
assert_eq!(option.replace(&42), None);
assert_eq!(option.replace(&420), Some(42));

Trait Implementations

impl<T> BorshDeserialize for LazyOption<T>where
    Vec<u8>: BorshDeserialize,

fn deserialize(buf: &mut &[u8]) -> Result<Self, Error>

Deserializes this instance from a given slice of bytes. Updates the buffer to point at the remaining bytes.

fn try_from_slice(v: &[u8]) -> Result<Self, Error>

Deserialize this instance from a slice of bytes.

impl<T> BorshSerialize for LazyOption<T>where
    Vec<u8>: BorshSerialize,

fn serialize<W: Write>(&self, writer: &mut W) -> Result<(), Error>

fn try_to_vec(&self) -> Result<Vec<u8, Global>, Error>

Serialize this instance into a vector of bytes.

impl<T> Debug for LazyOption<T>where
    T: Debug + BorshSerialize + BorshDeserialize,

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

Formats the value using the given formatter.