Introduce QMap key iterators

So we can have interoperability with algorithms.
Motivated by inefficient code like qDeleteAll(map.keys())

[ChangeLog][QtCore][QMap] Added key iterators, accessible through
keyBegin() and keyEnd().

Change-Id: Ieee2f9ad031e9d1e845a71447746699bbe95b96c
Reviewed-by: Marc Mutz <marc.mutz@kdab.com>

1 files changed, 28 insertions, 0 deletions

diff --git a/src/corelib/tools/qmap.h b/src/corelib/tools/qmap.h
index f3d921c968..b7bd268bda 100644
--- a/src/corelib/tools/qmap.h
+++ b/src/corelib/tools/qmap.h
@@ -518,6 +518,32 @@ public:
     };
     friend class const_iterator;
 
+    class key_iterator
+    {
+        const_iterator i;
+
+    public:
+        typedef typename const_iterator::iterator_category iterator_category;
+        typedef typename const_iterator::difference_type difference_type;
+        typedef Key value_type;
+        typedef const Key *pointer;
+        typedef const Key &reference;
+
+        explicit key_iterator(const_iterator o) : i(o) { }
+
+        const Key &operator*() const { return i.key(); }
+        const Key *operator->() const { return &i.key(); }
+        bool operator==(key_iterator o) const { return i == o.i; }
+        bool operator!=(key_iterator o) const { return i != o.i; }
+
+        inline key_iterator &operator++() { ++i; return *this; }
+        inline key_iterator operator++(int) { return key_iterator(i++);}
+        inline key_iterator &operator--() { --i; return *this; }
+        inline key_iterator operator--(int) { return key_iterator(i--); }
+        const_iterator base() const { return i; }
+    };
+
+
     // STL style
     inline iterator begin() { detach(); return iterator(d->begin()); }
     inline const_iterator begin() const { return const_iterator(d->begin()); }
@@ -527,6 +553,8 @@ public:
     inline const_iterator end() const { return const_iterator(d->end()); }
     inline const_iterator constEnd() const { return const_iterator(d->end()); }
     inline const_iterator cend() const { return const_iterator(d->end()); }
+    inline key_iterator keyBegin() const { return key_iterator(begin()); }
+    inline key_iterator keyEnd() const { return key_iterator(end()); }
     iterator erase(iterator it);
 
     // more Qt