# scopeguard
Rust crate for a convenient RAII scope guard that will run a given closure when
it goes out of scope, even if the code between panics (assuming unwinding panic).
The `defer!` macro and `guard` are `no_std` compatible (require only `core`),
but the on unwinding / not on unwinding strategies require linking to `std`.
By default, the `use_std` crate feature is enabled. Disable the default features
for `no_std` support.
Please read the [API documentation here](https://docs.rs/scopeguard/).
Minimum supported Rust version: 1.20
[](https://github.com/bluss/scopeguard/actions/workflows/ci.yaml)
[](https://crates.io/crates/scopeguard)
## How to use
```rs
#[macro_use(defer)]
extern crate scopeguard;
use scopeguard::guard;
fn f() {
defer! {
println!("Called at return or panic");
}
panic!();
}
use std::fs::File;
use std::io::Write;
fn g() {
let f = File::create("newfile.txt").unwrap();
let mut file = guard(f, |f| {
// write file at return or panic
let _ = f.sync_all();
});
// access the file through the scope guard itself
file.write_all(b"test me\n").unwrap();
}
```
## Recent Changes
- 1.2.0
- Use ManuallyDrop instead of mem::forget in into_inner. (by @willtunnels)
- Warn if the guard is not assigned to a variable and is dropped immediately
instead of at the scope's end. (by @sergey-v-galtsev)
- 1.1.0
- Change macros (`defer!`, `defer_on_success!` and `defer_on_unwind!`)
to accept statements. (by @konsumlamm)
- 1.0.0
- Change the closure type from `FnMut(&mut T)` to `FnOnce(T)`:
Passing the inner value by value instead of a mutable reference is a
breaking change, but allows the guard closure to consume it. (by @tormol)
- Add `defer_on_success!`, `guard_on_success()` and `OnSuccess`
strategy, which triggers when scope is exited *without* panic. It's the
opposite to `defer_on_unwind!` / `guard_on_unwind()` / `OnUnwind`.
- Add `ScopeGuard::into_inner()`, which "defuses" the guard and returns the
guarded value. (by @tormol)
- Implement `Sync` for guards with non-`Sync` closures.
- Require Rust 1.20
- 0.3.3
- Use `#[inline]` on a few more functions by @stjepang (#14)
- Add examples to crate documentation
- 0.3.2
- Add crate categories
- 0.3.1
- Add `defer_on_unwind!`, `Strategy` trait
- Rename `Guard` → `ScopeGuard`
- Add `ScopeGuard::with_strategy`.
- `ScopeGuard` now implements `Debug`.
- Require Rust 1.11
- 0.2.0
- Require Rust 1.6
- Use `no_std` unconditionally
- No other changes
- 0.1.2
- Add macro `defer!`