Add tag::as method

4 files changed, 30 insertions, 6 deletions

diff --git a/include/tag.h b/include/tag.h
index 58b99c082c..569da446d6 100644
--- a/include/tag.h
+++ b/include/tag.h
@@ -71,6 +71,15 @@ public:
     std::unique_ptr<tag> clone() &&;
 
     /**
+     * @brief Returns a reference to the tag as an instance of T
+     * @throw std::bad_cast if the tag is not of type T
+     */
+    template<class T>
+    T& as();
+    template<class T>
+    const T& as() const;
+
+    /**
      * @brief Move-assigns the given tag if the class is the same
      * @throw std::bad_cast if @c rhs is not the same type as @c *this
      */
@@ -101,6 +110,20 @@ private:
 
 std::ostream& operator<<(std::ostream& os, tag_type tt);
 
+template<class T>
+T& tag::as()
+{
+    static_assert(std::is_base_of<tag, T>::value, "T must be a subclass of tag");
+    return dynamic_cast<T&>(*this);
+}
+
+template<class T>
+const T& tag::as() const
+{
+    static_assert(std::is_base_of<tag, T>::value, "T must be a subclass of tag");
+    return dynamic_cast<const T&>(*this);
+}
+
 }
 
 #endif // TAG_H_INCLUDED
diff --git a/include/value.h b/include/value.h
index c017bcbd27..4865c8fd1c 100644
--- a/include/value.h
+++ b/include/value.h
@@ -93,7 +93,7 @@ public:
     const tag& get() const;
 
     /**
-     * @brief Returns the contained tag as an instance of T
+     * @brief Returns a reference to the contained tag as an instance of T
      * @throw std::bad_cast if the tag is not of type T
      */
     template<class T>
@@ -207,15 +207,13 @@ private:
 template<class T>
 T& value::as()
 {
-    static_assert(std::is_base_of<tag, T>::value, "T must be a subclass of tag");
-    return dynamic_cast<T&>(get());
+    return tag_->as<T>();
 }
 
 template<class T>
 const T& value::as() const
 {
-    static_assert(std::is_base_of<tag, T>::value, "T must be a subclass of tag");
-    return dynamic_cast<T&>(get());
+    return tag_->as<T>();;
 }
 
 }
diff --git a/test/io/read_test.cpp b/test/io/read_test.cpp
index aa731e1e55..d3ea8b7765 100644
--- a/test/io/read_test.cpp
+++ b/test/io/read_test.cpp
@@ -109,7 +109,7 @@ void test_read_bigtest()
     auto tagptr = reader.read_payload(tag_type::Compound);
 
     ASSERT(tagptr->get_type() == tag_type::Compound);
-    const tag_compound& comp = static_cast<const tag_compound&>(*tagptr);
+    const tag_compound& comp = tagptr->as<tag_compound>();
 
     ASSERT(comp.size() == 13);
 
diff --git a/test/nbttest.cpp b/test/nbttest.cpp
index 15b0c67fba..b041d44aa8 100644
--- a/test/nbttest.cpp
+++ b/test/nbttest.cpp
@@ -54,6 +54,9 @@ void test_tag()
     tstr.assign(tag_string("bar"));
     EXPECT_EXCEPTION(tstr.assign(tag_int(6)), std::bad_cast);
     ASSERT(tstr.get() == "bar");
+
+    ASSERT(&tstr.as<tag_string>() == &tstr);
+    EXPECT_EXCEPTION(tstr.as<tag_byte_array>(), std::bad_cast);
     std::clog << "test_tag passed" << std::endl;
 }