DropGuard in std::mem - Rust
Description: Wrap a value and run a closure when dropped.

## DropGuard

# Struct DropGuard

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    pub struct DropGuard<T, F>where
        F: FnOnce(T),{ /* private fields */ }

🔬This is a nightly-only experimental API. (`drop_guard` #144426)
Expand description

Wrap a value and run a closure when dropped.

This is useful for quickly creating destructors inline.

## §Examples

    #![feature(drop_guard)]

    use std::mem::DropGuard;

    {
        // Create a new guard around a string that will
        // print its value when dropped.
        let s = String::from("Chashu likes tuna");
        let mut s = DropGuard::new(s, |s| println!("{s}"));

        // Modify the string contained in the guard.
        s.push_str("!!!");

        // The guard will be dropped here, printing:
        // "Chashu likes tuna!!!"
    }

## Implementations§

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### impl<T, F> DropGuard<T, F>
where F: FnOnce(T),

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#### pub const fn new(inner: T, f: F) -> DropGuard<T, F>

🔬This is a nightly-only experimental API. (`drop_guard` #144426)

Create a new instance of `DropGuard`.

##### §Example

    #![feature(drop_guard)]

    use std::mem::DropGuard;

    let value = String::from("Chashu likes tuna");
    let guard = DropGuard::new(value, |s| println!("{s}"));

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#### pub const fn dismiss(guard: DropGuard<T, F>) -> T

🔬This is a nightly-only experimental API. (`drop_guard` #144426)

Consumes the `DropGuard`, returning the wrapped value.

This will not execute the closure. It is typically preferred to call this function instead of `mem::forget` because it will return the stored value and drop variables captured by the closure instead of leaking their owned resources.

##### §Example

    #![feature(drop_guard)]

    use std::mem::DropGuard;

    let value = String::from("Nori likes chicken");
    let guard = DropGuard::new(value, |s| println!("{s}"));
    assert_eq!(DropGuard::dismiss(guard), "Nori likes chicken");

## Trait Implementations§

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### impl<T, F> Debug for DropGuard<T, F>
where T: Debug, F: FnOnce(T),

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

Formats the value using the given formatter. Read more
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### impl<T, F> Deref for DropGuard<T, F>
where F: FnOnce(T),

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#### type Target = T

The resulting type after dereferencing.
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#### fn deref(&self) -> &T

Dereferences the value.
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### impl<T, F> DerefMut for DropGuard<T, F>
where F: FnOnce(T),

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#### fn deref_mut(&mut self) -> &mut T

Mutably dereferences the value.
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### impl<T, F> Drop for DropGuard<T, F>
where F: FnOnce(T),

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#### fn drop(&mut self)

Executes the destructor for this type. Read more

## Auto Trait Implementations§

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### impl<T, F> Freeze for DropGuard<T, F>
where T: Freeze, F: Freeze,

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### impl<T, F> RefUnwindSafe for DropGuard<T, F>
where T: RefUnwindSafe, F: RefUnwindSafe,

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### impl<T, F> Send for DropGuard<T, F>
where T: Send, F: Send,

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### impl<T, F> Sync for DropGuard<T, F>
where T: Sync, F: Sync,

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### impl<T, F> Unpin for DropGuard<T, F>
where T: Unpin, F: Unpin,

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### impl<T, F> UnwindSafe for DropGuard<T, F>
where T: UnwindSafe, F: UnwindSafe,

## Blanket Implementations§

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### impl<T> Any for T
where T: 'static + ?Sized,

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#### fn type_id(&self) -> TypeId

Gets the `TypeId` of `self`. Read more
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### impl<T> Borrow<T> for T
where T: ?Sized,

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#### fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more
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### impl<T> BorrowMut<T> for T
where T: ?Sized,

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#### fn borrow_mut(&mut self) -> &mut T

Mutably borrows from an owned value. Read more
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### impl<T> From<T> for T

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#### fn from(t: T) -> T

Returns the argument unchanged.

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### impl<T, U> Into<U> for T
where U: From<T>,

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#### fn into(self) -> U

Calls `U::from(self)`.

That is, this conversion is whatever the implementation of `From<T> for U` chooses to do.

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### impl<P, T> Receiver for P
where P: Deref<Target = T> + ?Sized, T: ?Sized,

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#### type Target = T

🔬This is a nightly-only experimental API. (`arbitrary_self_types` #44874)
The target type on which the method may be called.
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### impl<T, U> TryFrom<U> for T
where U: Into<T>,

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#### type Error = Infallible

The type returned in the event of a conversion error.
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#### fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>

Performs the conversion.
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### impl<T, U> TryInto<U> for T
where U: TryFrom<T>,

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

The type returned in the event of a conversion error.
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#### fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>

Performs the conversion.