fralalonde#42 Improve API, remove Arc that wraps the closure.

examples/observer.rs

@@ -20,7 +20,6 @@ extern crate dipstick;
 
 use std::fs::File;
 use std::io::{self, BufRead, BufReader};
-use std::sync::Arc;
 use std::time::{Duration, Instant};
 
 use dipstick::{AtomicBucket, InputScope, MetricValue, Prefixed, ScheduleFlush, Stream};
@@ -34,8 +33,8 @@ fn main() {
     metrics.set_drain(Stream::to_stderr());
     let flush_handle = metrics.flush_every(Duration::from_secs(1));
 
-    metrics.observe("uptime", Arc::new(move || dur2ms(start_time.elapsed())));
-    metrics.observe("threads", Arc::new(threads));
+    metrics.observe("uptime", move || dur2ms(start_time.elapsed()));
+    metrics.observe("threads", threads);
 
     println!("Press Enter key to exit");
     io::stdin().read_line(&mut String::new()).expect("Example, ignored");

src/bucket/atomic.rs

@@ -232,7 +232,7 @@ impl InputScope for AtomicBucket {
         InputMetric::new(move |value, _labels| scores.update(value))
     }
 
-    fn observe(&self, name: &str, callback: GaugeCallback) {
+    fn observe_helper(&self, name: &str, callback: GaugeCallback) {
         let gauge = self.gauge(name);
 
         self.inner

src/core/input.rs

@@ -66,7 +66,13 @@ pub trait InputScope: Flush {
 
     /// Observe a gauge value using a callback function. If multiple callbacks are registered under
     /// the same conflicting key, only the last one will survive.
-    fn observe(&self, _name: &str, _callback: GaugeCallback) {
+    fn observe<F: Fn() -> MetricValue + Send + Sync + 'static>(&self, name: &str, callback: F) where Self: Sized {
+        self.observe_helper(name, Arc::new(callback));
+    }
+
+    /// Helper method to make use of `observe()` more pleasant. The Arc wrapper is not necessary
+    /// in the client code now. Consider this as an internal method.
+    fn observe_helper(&self, _name: &str, _callback: GaugeCallback) {
         // TODO: Not yet finished, remove default impl.
     }
 }
@@ -190,7 +196,7 @@ impl Gauge {
 }
 
 /// Callback function for gauge observer.
-pub type GaugeCallback = Arc<Fn() -> MetricValue + Send + Sync>;
+pub(crate) type GaugeCallback = Arc<Fn() -> MetricValue + Send + Sync + 'static>;
 
 /// Gauge and it's observer callback.
 #[derive(Clone)]