mcmp: make InheritedValue a function, not a method, and add Parent method to support it

mcmp/component.go

@@ -69,20 +69,6 @@ func (c *Component) Value(key interface{}) interface{} {
 	return value
 }
 
-// InheritedValue returns the value which has been set for the given key. It first
-// looks for the key on the receiver Component. If not found, it will look on
-// its parent Component, and so on, until the key is found. If the key is not
-// found on the root Component then false is returned.
-func (c *Component) InheritedValue(key interface{}) (interface{}, bool) {
-	value, ok := c.value(key)
-	if ok {
-		return value, ok
-	} else if c.parent == nil {
-		return nil, false
-	}
-	return c.parent.InheritedValue(key)
-}
-
 // Values returns all key/value pairs which have been set via SetValue.
 func (c *Component) Values() map[interface{}]interface{} {
 	c.l.RLock()
@@ -137,6 +123,13 @@ func (c *Component) Children() []*Component {
 	return children
 }
 
+// Parent returns the Component from which this one was created via the Child
+// method. This returns nil if this Component was not created via Child (and is
+// therefore the root Component).
+func (c *Component) Parent() *Component {
+	return c.parent
+}
+
 // Name returns the name this Component was created with (via the Child method),
 // or false if this Component was not created via Child (and is therefore the
 // root Component).
@@ -216,3 +209,17 @@ func BreadthFirstVisit(c *Component, callback func(*Component) bool) {
 		queue = queue[1:]
 	}
 }
+
+// InheritedValue returns the value which has been set for the given key. It
+// first looks for the key on the receiver Component. If not found, it will look
+// on its parent Component, and so on, until the key is found. If the key is not
+// found on any Components, up to the root Component, then false is returned.
+func InheritedValue(c *Component, key interface{}) (interface{}, bool) {
+	if c.HasValue(key) {
+		return c.kv[key], true
+	} else if parent := c.Parent(); parent == nil {
+		return nil, false
+	} else {
+		return InheritedValue(parent, key)
+	}
+}

mcmp/component_test.go

@@ -53,23 +53,6 @@ func TestComponent(t *T) {
 		assertValue(child, "bar", 2),
 	)
 
-	assertInheritedValue := func(c *Component, key, expectedValue interface{}) massert.Assertion {
-		val, ok := c.InheritedValue(key)
-		return massert.All(
-			massert.Equal(expectedValue, val),
-			massert.Equal(expectedValue != nil, ok),
-		)
-	}
-
-	// test that InheritedValue does what it's supposed to
-	massert.Require(t,
-		assertInheritedValue(c, "foo", 1),
-		assertInheritedValue(child, "foo", 1),
-		assertInheritedValue(c, "bar", nil),
-		assertInheritedValue(child, "bar", 2),
-		assertInheritedValue(c, "xxx", nil),
-		assertInheritedValue(child, "xxx", nil),
-	)
 }
 func TestBreadFirstVisit(t *T) {
 	cmp := new(Component)
@@ -103,3 +86,29 @@ func TestBreadFirstVisit(t *T) {
 		)
 	}
 }
+
+func TestInheritedValue(t *T) {
+
+	assertInheritedValue := func(c *Component, key, expectedValue interface{}) massert.Assertion {
+		val, ok := InheritedValue(c, key)
+		return massert.All(
+			massert.Equal(expectedValue, val),
+			massert.Equal(expectedValue != nil, ok),
+		)
+	}
+
+	c := new(Component)
+	c.SetValue("foo", 1)
+	child := c.Child("child")
+	child.SetValue("bar", 2)
+
+	// test that InheritedValue does what it's supposed to
+	massert.Require(t,
+		assertInheritedValue(c, "foo", 1),
+		assertInheritedValue(child, "foo", 1),
+		assertInheritedValue(c, "bar", nil),
+		assertInheritedValue(child, "bar", 2),
+		assertInheritedValue(c, "xxx", nil),
+		assertInheritedValue(child, "xxx", nil),
+	)
+}