# Struct once_cell::sync::Lazy [−] [src]

    pub struct Lazy<T, F = fn() -> T> { /* fields omitted */ }

A value which is initialized on the first access.

This type is thread-safe and can be used in statics.

# Example

    use std::collections::HashMap;

    use once_cell::sync::Lazy;

    static HASHMAP: Lazy<HashMap<i32, String>> = Lazy::new(|| {
        println!("initializing");
        let mut m = HashMap::new();
        m.insert(13, "Spica".to_string());
        m.insert(74, "Hoyten".to_string());
        m
    });

    fn main() {
        println!("ready");
        std::thread::spawn(|| {
            println!("{:?}", HASHMAP.get(&13));
        }).join().unwrap();
        println!("{:?}", HASHMAP.get(&74));

        // Prints:
        //   ready
        //   initializing
        //   Some("Spica")
        //   Some("Hoyten")
    }

## Implementations

### `impl<T, F> Lazy<T, F>` [src]

#### `pub const fn new(f: F) -> Lazy<T, F>` [src]

Creates a new lazy value with the given initializing function.

#### `pub fn into_value(this: Lazy<T, F>) -> Result<T, F>` [src]

Consumes this `Lazy` returning the stored value.

Returns `Ok(value)` if `Lazy` is initialized and `Err(f)` otherwise.

### `impl<T, F: FnOnce() -> T> Lazy<T, F>` [src]

#### `pub fn force(this: &Lazy<T, F>) -> &T` [src]

Forces the evaluation of this lazy value and returns a reference to the result. This is equivalent to the `Deref` impl, but is explicit.

# Example

    use once_cell::sync::Lazy;

    let lazy = Lazy::new(|| 92);

    assert_eq!(Lazy::force(&lazy), &92);
    assert_eq!(&*lazy, &92);

## Trait Implementations

### `impl<T: Debug, F> Debug for Lazy<T, F>` [src]

#### `fn fmt(&self, f: &mut Formatter<'_>) -> Result` [src]

Formats the value using the given formatter. Read more

### `impl<T: Default> Default for Lazy<T>` [src]

#### `fn default() -> Lazy<T>` [src]

Creates a new lazy value using `Default` as the initializing function.

### `impl<T, F: FnOnce() -> T> Deref for Lazy<T, F>` [src]

#### `type Target = T`

The resulting type after dereferencing.

#### `fn deref(&self) -> &T` [src]

Dereferences the value.

### `impl<T, F: FnOnce() -> T> DerefMut for Lazy<T, F>` [src]

#### `fn deref_mut(&mut self) -> &mut T` [src]

Mutably dereferences the value.

### `impl<T, F: RefUnwindSafe> RefUnwindSafe for Lazy<T, F> where
OnceCell<T>: RefUnwindSafe,` [src]

### `impl<T, F: Send> Sync for Lazy<T, F> where
OnceCell<T>: Sync,` [src]

## Auto Trait Implementations

### `impl<T, F> Send for Lazy<T, F> where
F: Send,
T: Send,`

### `impl<T, F> Unpin for Lazy<T, F> where
F: Unpin,
T: Unpin,`

### `impl<T, F> UnwindSafe for Lazy<T, F> where
F: UnwindSafe,
T: UnwindSafe,`

## Blanket Implementations

### `impl<T> Any for T where
T: 'static + ?Sized,` [src]

#### `pub fn type_id(&self) -> TypeId` [src]

Gets the `TypeId` of `self`. Read more

### `impl<T> Borrow<T> for T where
T: ?Sized,` [src]

#### `pub fn borrow(&self) -> &T` [src]

Immutably borrows from an owned value. Read more

### `impl<T> BorrowMut<T> for T where
T: ?Sized,` [src]

#### `pub fn borrow_mut(&mut self) -> &mut T` [src]

Mutably borrows from an owned value. Read more

### `impl<T> From<T> for T` [src]

#### `pub fn from(t: T) -> T` [src]

Performs the conversion.

### `impl<T, U> Into<U> for T where
U: From<T>,` [src]

#### `pub fn into(self) -> U` [src]

Performs the conversion.

### `impl<T, U> TryFrom<U> for T where
U: Into<T>,` [src]

#### `type Error = Infallible`

The type returned in the event of a conversion error.

#### `pub fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>` [src]

Performs the conversion.

### `impl<T, U> TryInto<U> for T where
U: TryFrom<T>,` [src]

#### `type Error = <U as TryFrom<T>>::Error`

The type returned in the event of a conversion error.

#### `pub fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>` [src]

Performs the conversion.