Add an easy way to get a particular component from an entity

Change-Id: I188fab5019d3e05354a4c1582fb12097a569fbb8
Reviewed-by: Mike Krus <mike.krus@kdab.com>

3 files changed, 53 insertions, 0 deletions

diff --git a/src/core/nodes/qentity.cpp b/src/core/nodes/qentity.cpp
index 64ea65087..3c8805a67 100644
--- a/src/core/nodes/qentity.cpp
+++ b/src/core/nodes/qentity.cpp
@@ -77,6 +77,13 @@ namespace Qt3DCore {
     \sa Qt3DCore::QComponent, Qt3DCore::QTransform
  */
 
+/*!
+    \fn template<typename T> QVector<T *> QEntity::componentsOfType() const
+
+    Returns all the components added to this entity that can be cast to
+    type T or an empty vector if there are no such components.
+*/
+
 /*! \internal */
 QEntityPrivate::QEntityPrivate()
     : QNodePrivate()
diff --git a/src/core/nodes/qentity.h b/src/core/nodes/qentity.h
index dc7dc62c1..ef6aedc4d 100644
--- a/src/core/nodes/qentity.h
+++ b/src/core/nodes/qentity.h
@@ -62,6 +62,19 @@ public:
 
     QComponentVector components() const;
 
+    template<class T>
+    QVector<T *> componentsOfType() const
+    {
+        QVector<T*> matchComponents;
+        const QComponentVector components = this->components();
+        for (QComponent *component : components) {
+            T *typedComponent = qobject_cast<T*>(component);
+            if (typedComponent != nullptr)
+                matchComponents.append(typedComponent);
+        }
+        return matchComponents;
+    }
+
     void addComponent(QComponent *comp);
     void removeComponent(QComponent *comp);
 
diff --git a/tests/auto/core/qentity/tst_qentity.cpp b/tests/auto/core/qentity/tst_qentity.cpp
index e27cd1fc9..d7847342b 100644
--- a/tests/auto/core/qentity/tst_qentity.cpp
+++ b/tests/auto/core/qentity/tst_qentity.cpp
@@ -53,6 +53,8 @@ private slots:
     void addComponentsSeveralParentsSingleAggregations();
     void addComponentsSeveralParentsSeveralAggregations();
 
+    void retrieveSingleComponent();
+
     void removeComponentSingleParentSingleAggregation();
     void removeComponentSingleParentSeveralAggregations();
     void removeComponentsSeveralParentsSingleAggreation();
@@ -76,6 +78,14 @@ public:
     {}
 };
 
+class MyQ2Component : public Qt3DCore::QComponent
+{
+    Q_OBJECT
+public:
+    explicit MyQ2Component(Qt3DCore::QNode *parent = 0)
+        : QComponent(parent)
+    {}
+};
 
 class MyEntity : public Qt3DCore::QEntity
 {
@@ -504,6 +514,29 @@ void tst_Entity::removeComponentsSeveralParentsSeveralAggregations()
     QCOMPARE(comp3->entities().size(), 0);
 }
 
+void tst_Entity::retrieveSingleComponent()
+{
+    // GIVEN
+    QScopedPointer<Qt3DCore::QEntity> entity1(new QEntity());
+
+    MyQComponent *comp1 = new MyQComponent(entity1.data());
+    MyQComponent *comp2 = new MyQComponent(entity1.data());
+    QCoreApplication::processEvents();
+    entity1->addComponent(comp1);
+    entity1->addComponent(comp2);
+
+    // WHEN
+    QVector<MyQComponent*> myQComponentsInEntity = entity1->componentsOfType<MyQComponent>();
+    QVector<MyQ2Component*> myQ2ComponentsInEntity = entity1->componentsOfType<MyQ2Component>();
+
+    // THEN
+    QVERIFY(myQComponentsInEntity.size() == 2);
+    QVERIFY(myQComponentsInEntity[0] == comp1);
+    QVERIFY(myQComponentsInEntity[1] == comp2);
+
+    QVERIFY(myQ2ComponentsInEntity.size() == 0);
+}
+
 void tst_Entity::addSeveralTimesSameComponent()
 {
     // GIVEN