Utils: Introduce TreeItem::{begin,end}

... and use this to reduce the number of explicit uses of m_children.

Despite of being shorter code by itself it is a step towards having
an explicit LeafItem object that doesn't explicitly store a(n empty)
vector of child nodes.

Change-Id: If8db85e2f1134dd1578a78d31235bf57a28f863a
Reviewed-by: Eike Ziller <eike.ziller@qt.io>

src/libs/utils/treemodel.cpp

@@ -620,7 +620,13 @@ TreeItem::~TreeItem()
 TreeItem *TreeItem::childAt(int pos) const
 {
     QTC_ASSERT(pos >= 0, return 0);
-    return pos < m_children.size() ? m_children.at(pos) : 0;
+    return pos < childCount() ? *(begin() + pos) : nullptr;
+}
+
+int TreeItem::indexOf(const TreeItem *item) const
+{
+    auto it = std::find(begin(), end(), item);
+    return it == end() ? -1 : it - begin();
 }
 
 QVariant TreeItem::data(int column, int role) const
@@ -661,14 +667,14 @@ void TreeItem::prependChild(TreeItem *item)
 
 void TreeItem::appendChild(TreeItem *item)
 {
-    insertChild(m_children.size(), item);
+    insertChild(childCount(), item);
 }
 
 void TreeItem::insertChild(int pos, TreeItem *item)
 {
     QTC_CHECK(!item->model());
     QTC_CHECK(!item->parent());
-    QTC_ASSERT(0 <= pos && pos <= m_children.size(), return); // '<= size' is intentional.
+    QTC_ASSERT(0 <= pos && pos <= childCount(), return); // '<=' is intentional.
 
     if (m_model) {
         QModelIndex idx = index();
@@ -733,7 +739,7 @@ void TreeItem::updateAll()
     if (m_model) {
         QModelIndex idx = index();
         m_model->dataChanged(idx, idx.sibling(idx.row(), m_model->m_columnCount - 1));
-        foreach (TreeItem *item, m_children)
+        for (TreeItem *item : *this)
             item->updateAll();
     }
 }
@@ -748,12 +754,12 @@ void TreeItem::updateColumn(int column)
 
 TreeItem *TreeItem::firstChild() const
 {
-    return m_children.isEmpty() ? 0 : m_children.first();
+    return childCount() == 0 ? nullptr : *begin();
 }
 
 TreeItem *TreeItem::lastChild() const
 {
-    return m_children.isEmpty() ? 0 : m_children.last();
+    return childCount() == 0 ? nullptr : *(end() - 1);
 }
 
 int TreeItem::level() const
@@ -766,7 +772,7 @@ int TreeItem::level() const
 
 int TreeItem::indexInParent() const
 {
-    return m_parent ? m_parent->m_children.indexOf(const_cast<TreeItem *>(this)) : -1;
+    return m_parent ? m_parent->indexOf(this) : -1;
 }
 
 QModelIndex TreeItem::index() const
@@ -782,7 +788,7 @@ QAbstractItemModel *TreeItem::model() const
 
 void TreeItem::forAllChildren(const std::function<void (TreeItem *)> &pred) const
 {
-    foreach (TreeItem *item, m_children) {
+    for (TreeItem *item : *this) {
         pred(item);
         item->forAllChildren(pred);
     }
@@ -790,7 +796,7 @@ void TreeItem::forAllChildren(const std::function<void (TreeItem *)> &pred) cons
 
 void TreeItem::forSelectedChildren(const std::function<bool (TreeItem *)> &pred) const
 {
-    foreach (TreeItem *item, m_children) {
+    for (TreeItem *item : *this) {
         if (pred(item))
             item->forSelectedChildren(pred);
     }
@@ -800,10 +806,10 @@ void TreeItem::forChildrenAtLevel(int level, const std::function<void(TreeItem *
 {
     QTC_ASSERT(level > 0, return);
     if (level == 1) {
-        foreach (TreeItem *item, m_children)
+        for (TreeItem *item : *this)
             pred(item);
     } else {
-        foreach (TreeItem *item, m_children)
+        for (TreeItem *item : *this)
             item->forChildrenAtLevel(level - 1, pred);
     }
 }
@@ -812,11 +818,11 @@ TreeItem *TreeItem::findChildAtLevel(int level, const std::function<bool(TreeIte
 {
     QTC_ASSERT(level > 0, return 0);
     if (level == 1) {
-        foreach (TreeItem *item, m_children)
+        for (TreeItem *item : *this)
             if (pred(item))
                 return item;
     } else {
-        foreach (TreeItem *item, m_children) {
+        for (TreeItem *item : *this) {
             if (auto found = item->findChildAtLevel(level - 1, pred))
                 return found;
         }
@@ -826,7 +832,7 @@ TreeItem *TreeItem::findChildAtLevel(int level, const std::function<bool(TreeIte
 
 TreeItem *TreeItem::findAnyChild(const std::function<bool(TreeItem *)> &pred) const
 {
-    foreach (TreeItem *item, m_children) {
+    for (TreeItem *item : *this) {
         if (pred(item))
             return item;
         if (TreeItem *found = item->findAnyChild(pred))
@@ -837,7 +843,7 @@ TreeItem *TreeItem::findAnyChild(const std::function<bool(TreeItem *)> &pred) co
 
 void TreeItem::clear()
 {
-    while (m_children.size()) {
+    while (childCount() != 0) {
         TreeItem *item = m_children.takeLast();
         item->m_model = 0;
         item->m_parent = 0;
@@ -857,7 +863,7 @@ void TreeItem::propagateModel(BaseTreeModel *m)
     QTC_ASSERT(m_model == 0 || m_model == m, return);
     if (m && !m_model) {
         m_model = m;
-        foreach (TreeItem *item, m_children)
+        for (TreeItem *item : *this)
             item->propagateModel(m);
     }
 }
@@ -1067,7 +1073,7 @@ QModelIndex BaseTreeModel::indexForItem(const TreeItem *item) const
     QTC_ASSERT(p, return QModelIndex());
 
     TreeItem *mitem = const_cast<TreeItem *>(item);
-    int row = p->m_children.indexOf(mitem);
+    int row = p->indexOf(mitem);
     return createIndex(row, 0, mitem);
 }
 
@@ -1095,7 +1101,7 @@ TreeItem *BaseTreeModel::takeItem(TreeItem *item)
     QTC_ASSERT(item, return item);
     TreeItem *parent = item->parent();
     QTC_ASSERT(parent, return item);
-    int pos = parent->m_children.indexOf(item);
+    int pos = parent->indexOf(item);
     QTC_ASSERT(pos != -1, return item);
 
     QModelIndex idx = indexForItem(parent);