Add From<&[T]> for Classes (#1448)

* Add From<&[T]> for Classes

* Round out the test cases for From<&[T]> for Classes

yew/src/virtual_dom/mod.rs

@@ -155,6 +155,12 @@ impl<T: AsRef<str>> From<&Option<T>> for Classes {
 
 impl<T: AsRef<str>> From<Vec<T>> for Classes {
     fn from(t: Vec<T>) -> Self {
+        Classes::from(t.as_slice())
+    }
+}
+
+impl<T: AsRef<str>> From<&[T]> for Classes {
+    fn from(t: &[T]) -> Self {
         let set = t
             .iter()
             .map(|x| x.as_ref())

yew/src/virtual_dom/vtag.rs

@@ -750,6 +750,38 @@ mod tests {
         }
     }
 
+    #[test]
+    fn supports_multiple_classes_slice() {
+        let classes = ["class-1", "class-2"];
+        let a = html! {
+            <div class=&classes[..]></div>
+        };
+
+        if let VNode::VTag(vtag) = a {
+            assert!(get_class_str(&vtag).contains("class-1"));
+            assert!(get_class_str(&vtag).contains("class-2"));
+            assert!(!get_class_str(&vtag).contains("class-3"));
+        } else {
+            panic!("vtag expected");
+        }
+    }
+
+    #[test]
+    fn supports_multiple_classes_one_value_slice() {
+        let classes = ["class-1 class-2", "class-1"];
+        let a = html! {
+            <div class=&classes[..]></div>
+        };
+
+        if let VNode::VTag(vtag) = a {
+            assert!(get_class_str(&vtag).contains("class-1"));
+            assert!(get_class_str(&vtag).contains("class-2"));
+            assert!(!get_class_str(&vtag).contains("class-3"));
+        } else {
+            panic!("vtag expected");
+        }
+    }
+
     #[test]
     fn supports_multiple_classes_vec() {
         let mut classes = vec!["class-1"];
@@ -784,12 +816,12 @@ mod tests {
     }
 
     #[test]
-    fn filter_empty_string_classes_vec() {
+    fn filter_empty_string_classes() {
-        let mut classes = vec![""];
-        classes.push("class-2");
         let a = html! { <div class=vec![""]></div> };
         let b = html! { <div class=("")></div> };
         let c = html! { <div class=""></div> };
+        let d_arr = [""];
+        let d = html! { <div class=&d_arr[..]></div> };
 
         if let VNode::VTag(vtag) = a {
             assert!(!vtag.attributes.contains_key("class"));
@@ -808,6 +840,12 @@ mod tests {
         } else {
             panic!("vtag expected");
         }
+
+        if let VNode::VTag(vtag) = d {
+            assert!(!vtag.attributes.contains_key("class"));
+        } else {
+            panic!("vtag expected");
+        }
     }
 
     fn assert_vtag(node: &mut VNode) -> &mut VTag {