add code sample

fsrc-example/src/bin/test2.rs

@@ -0,0 +1,54 @@
+use std::sync::{Arc, Mutex};
+
+trait ProvidesFoo {
+    fn magic(&mut self);
+}
+
+struct Foo {
+    magic_value: u32
+}
+
+impl Default for Foo {
+    fn default() -> Self {
+        Self {magic_value: 42}
+    }
+}
+
+impl ProvidesFoo for Foo {
+    fn magic(&mut self) {
+        println!("ProvidesFoo magic");
+    }
+}
+
+pub type SharedFooConcrete = Arc<Mutex<Box<Foo>>>;
+pub type SharedFooTraitObj = Arc<Mutex<Box<dyn ProvidesFoo + Send + Sync>>>;
+
+struct FooProvider {
+    foo_as_trait_obj: SharedFooTraitObj
+
+}
+
+impl FooProvider {
+    fn magic_and_then_some(&mut self) {
+        let mut fooguard = self.foo_as_trait_obj.lock().unwrap();
+        fooguard.magic();
+        println!("Additional magic");
+    }
+}
+
+fn uses_shared_foo_boxed_trait_obj(foo: SharedFooTraitObj) {
+    let mut foo_provider = FooProvider {
+        foo_as_trait_obj: foo
+    };
+    foo_provider.magic_and_then_some();
+}
+fn uses_shared_foo_concrete(foo: SharedFooConcrete) {
+    let mut fooguard = foo.lock().unwrap();
+    fooguard.magic();
+}
+
+fn main() {
+    let shared_foo = Arc::new(Mutex::new(Box::new(Foo::default())));
+    uses_shared_foo_concrete(shared_foo.clone());
+    uses_shared_foo_boxed_trait_obj(shared_foo);
+}