attention: Replace parse_* and serialise with TryFrom<Element> and Into<Element>.

src/attention.rs

@@ -4,6 +4,8 @@
 // License, v. 2.0. If a copy of the MPL was not distributed with this
 // file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
+use std::convert::TryFrom;
+
 use minidom::Element;
 
 use error::Error;
@@ -13,38 +15,45 @@ use ns;
 #[derive(Debug, Clone)]
 pub struct Attention;
 
-pub fn parse_attention(root: &Element) -> Result<Attention, Error> {
-    if !root.is("attention", ns::ATTENTION) {
-        return Err(Error::ParseError("This is not an attention element."));
+impl<'a> TryFrom<&'a Element> for Attention {
+    type Error = Error;
+
+    fn try_from(elem: &'a Element) -> Result<Attention, Error> {
+        if !elem.is("attention", ns::ATTENTION) {
+            return Err(Error::ParseError("This is not an attention element."));
+        }
+        for _ in elem.children() {
+            return Err(Error::ParseError("Unknown child in attention element."));
+        }
+        Ok(Attention)
     }
-    for _ in root.children() {
-        return Err(Error::ParseError("Unknown child in attention element."));
-    }
-    Ok(Attention)
 }
 
-pub fn serialise(_: &Attention) -> Element {
-    Element::builder("attention")
-            .ns(ns::ATTENTION)
-            .build()
+impl<'a> Into<Element> for &'a Attention {
+    fn into(self) -> Element {
+        Element::builder("attention")
+                .ns(ns::ATTENTION)
+                .build()
+    }
 }
 
 #[cfg(test)]
 mod tests {
+    use std::convert::TryFrom;
     use minidom::Element;
     use error::Error;
-    use attention;
+    use super::Attention;
 
     #[test]
     fn test_simple() {
         let elem: Element = "<attention xmlns='urn:xmpp:attention:0'/>".parse().unwrap();
-        attention::parse_attention(&elem).unwrap();
+        Attention::try_from(&elem).unwrap();
     }
 
     #[test]
     fn test_invalid_child() {
         let elem: Element = "<attention xmlns='urn:xmpp:attention:0'><coucou/></attention>".parse().unwrap();
-        let error = attention::parse_attention(&elem).unwrap_err();
+        let error = Attention::try_from(&elem).unwrap_err();
         let message = match error {
             Error::ParseError(string) => string,
             _ => panic!(),
@@ -55,8 +64,10 @@ mod tests {
     #[test]
     fn test_serialise() {
         let elem: Element = "<attention xmlns='urn:xmpp:attention:0'/>".parse().unwrap();
-        let attention = attention::Attention;
-        let elem2 = attention::serialise(&attention);
+        let attention = Attention;
+        let elem2: Element = (&attention).into();
+        let elem3: Element = (&attention).into();
         assert_eq!(elem, elem2);
+        assert_eq!(elem2, elem3);
     }
 }