Add example of passing dyn trait instance

Cargo.toml

@@ -139,3 +139,7 @@ required-features = ["async", "proc_macro"]
 [[example]]
 name = "expiring_sized_cache"
 required-features = ["async_tokio_rt_multi_thread"]
+
+[[example]]
+name = "dyn_trait_pass"
+required-features = [ "default" ]

examples/dyn_trait_pass.rs

@@ -0,0 +1,62 @@
+use cached::proc_macro::cached;
+use thiserror::Error;
+
+#[allow(dead_code)]
+#[derive(Error, Debug, PartialEq, Clone)]
+enum ProcessorError {
+    #[error("error wile processing task :{0}")]
+    TaskError(String),
+}
+
+trait AnyTaskProcessor {
+    type Error;
+
+    fn execute(&self) -> Result<String, ProcessorError>;
+}
+
+struct CustomProcessor;
+
+impl AnyTaskProcessor for CustomProcessor {
+    type Error = ProcessorError;
+
+    fn execute(&self) -> Result<String, Self::Error> {
+        Ok(String::from("hello world"))
+    }
+}
+
+#[cached(
+    time = 100,             // Expires after 100 seconds
+    size = 1,               // Cache size (1) elements
+    result = true,          // Cache the Result type
+    key = "i32",            // Necessary option for caching method result
+    convert = r##"{ 1 }"##  // Necessary option for key -> used static integer for example only
+)]
+fn cached_execute(
+    processor: &(dyn AnyTaskProcessor<Error = ProcessorError> + Send + Sync),
+) -> Result<String, ProcessorError> {
+    std::thread::sleep(std::time::Duration::from_secs(2));
+    let result = processor.execute()?;
+    Ok(result)
+}
+
+fn main() -> Result<(), Box<dyn std::error::Error>> {
+    let mean_delay = 100u128;
+
+    let custom_processor = CustomProcessor {};
+
+    let start_time = std::time::Instant::now();
+    let result = cached_execute(&custom_processor)?;
+    let elapsed = start_time.elapsed();
+    assert_eq!(&result, "hello world");
+    assert!(elapsed.as_millis() >= mean_delay);
+
+    let start_time = std::time::Instant::now();
+    let result = cached_execute(&custom_processor)?;
+    let elapsed = start_time.elapsed();
+    assert_eq!(&result, "hello world");
+    assert!(elapsed.as_millis() < mean_delay);
+
+    println!("done!");
+
+    Ok(())
+}