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-rw-r--r--fun/defer_rs/examples/undefer.rs40
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diff --git a/fun/defer_rs/examples/undefer.rs b/fun/defer_rs/examples/undefer.rs
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+// Go's defer in Rust, with a little twist!
+
+struct Defer<F: Fn()> {
+    f: F,
+}
+
+impl<F: Fn()> Drop for Defer<F> {
+    fn drop(&mut self) {
+        (self.f)()
+    }
+}
+
+// Only added this for Go-syntax familiarity ;-)
+fn defer<F: Fn()>(f: F) -> Defer<F> {
+    Defer { f }
+}
+
+// Changed your mind about the defer?
+// (Note: This leaks the closure! Don't actually do this!)
+fn undefer<F: Fn()>(token: Defer<F>) {
+    use std::mem;
+    mem::forget(token);
+}
+
+fn main() {
+    let mut i = 1;
+
+    // Calling it "token" ... could be something else. The lifetime of this
+    // controls when the action is run.
+    let token = defer(move || println!("Value is: {}", i));
+
+    i += 1;
+    println!("Value is: {}", i);
+
+    // Oh, now I changed my mind about the previous defer:
+    undefer(token);
+}
+
+// Prints:
+// Value is: 2