BUG: Fix printing of values in MetaDataObject

Also removes dead code related to METADATAPRINT

Fix #1454

Co-Author: Pablo Hernandez-Cerdan <[email protected]>

Author: blowekamp

Modules/Core/Common/include/itkMetaDataObject.h

@@ -58,15 +58,8 @@ namespace itk
  * and redefining the copy constructor and initializing constructor and the Get/Set functions
  * to work around those deficiencies.
  *
- * The behavior of the MetaDataObject<Type>::Print() function has many plausible
- * application dependent implementations.  The default implementation prints the
- * string "[UNKNOWN PRINT CHARACTERISTICS]" that works for all possible
- * MetaDataObject types.
- *
- * The application developer may overload the default implementation to provide
- * a specialized Print() characteristics to produce results desirable for their application.
- * A set of very crude Macros {NATIVE_TYPE_METADATAPRINT, ITK_OBJECT_TYPE_METADATAPRINT_1COMMA,
- * ITK_IMAGE_TYPE_METADATAPRINT  } are provided to facilitate a very simple implementation, and as an example.
+ * The default implementation prints uses the MetaDataObjectType's Print or operator<< if available. Otherwise, it
+ * prints string "[UNKNOWN PRINT CHARACTERISTICS]".
  *
  * \ingroup ITKCommon
  *
@@ -264,52 +257,6 @@ ExposeMetaData(const MetaDataDictionary & Dictionary, const std::string key, T &
 
 } // end namespace itk
 
-/**
- * \def ITK_NATIVE_TYPE_METADATAPRINT( TYPE_NAME )
- * \brief An ugly macro to facilitate creating a simple implementation of
- * the MetaDataObject<Type>::Print() function for types that
- * have operator<< defined.
- * \param TYPE_NAME the native type parameter type
- */
-#define ITK_NATIVE_TYPE_METADATAPRINT(TYPE_NAME)                      \
-  template <>                                                         \
-  void itk::MetaDataObject<TYPE_NAME>::Print(std::ostream & os) const \
-  {                                                                   \
-    os << this->m_MetaDataObjectValue << std::endl;                   \
-  }
-
-/**
- * \def ITK_OBJECT_TYPE_METADATAPRINT_1COMMA( TYPE_NAME_PART1, TYPE_NAME_PART2 )
- * \brief An ugly macro to facilitate creating a simple implementation of
- * the MetaDataObject< Type >::Print() function for
- * itk::Objects that have 1 comma in their type definition
- * \param TYPE_NAME_PART1
- * \param TYPE_NAME_PART2
- */
-#define ITK_OBJECT_TYPE_METADATAPRINT_1COMMA(TYPE_NAME_PART1, TYPE_NAME_PART2)               \
-  template <>                                                                                \
-  void itk::MetaDataObject<TYPE_NAME_PART1, TYPE_NAME_PART2>::Print(std::ostream & os) const \
-  {                                                                                          \
-    this->m_MetaDataObjectValue->Print(os);                                                  \
-  }
-
-/**
- * \def ITK_IMAGE_TYPE_METADATAPRINT( STORAGE_TYPE )
- * An ugly macro to facilitate creating a simple implementation of
- * the MetaDataObject<Type>::Print() function for
- * itk::Image\<STORAGE_TYPE,[1-8]\>\::Pointer
- * \param STORAGE_TYPE The storage type of the image type to print.
- */
-#define ITK_IMAGE_TYPE_METADATAPRINT(STORAGE_TYPE)                           \
-  ITK_OBJECT_TYPE_METADATAPRINT_1COMMA(itk::Image<STORAGE_TYPE, 1>::Pointer) \
-  ITK_OBJECT_TYPE_METADATAPRINT_1COMMA(itk::Image<STORAGE_TYPE, 2>::Pointer) \
-  ITK_OBJECT_TYPE_METADATAPRINT_1COMMA(itk::Image<STORAGE_TYPE, 3>::Pointer) \
-  ITK_OBJECT_TYPE_METADATAPRINT_1COMMA(itk::Image<STORAGE_TYPE, 4>::Pointer) \
-  ITK_OBJECT_TYPE_METADATAPRINT_1COMMA(itk::Image<STORAGE_TYPE, 5>::Pointer) \
-  ITK_OBJECT_TYPE_METADATAPRINT_1COMMA(itk::Image<STORAGE_TYPE, 6>::Pointer) \
-  ITK_OBJECT_TYPE_METADATAPRINT_1COMMA(itk::Image<STORAGE_TYPE, 7>::Pointer) \
-  ITK_OBJECT_TYPE_METADATAPRINT_1COMMA(itk::Image<STORAGE_TYPE, 8>::Pointer)
-
 #ifndef ITK_MANUAL_INSTANTIATION
 #  include "itkMetaDataObject.hxx"
 #endif

Modules/Core/Common/include/itkMetaDataObject.hxx

@@ -59,11 +59,45 @@ MetaDataObject<MetaDataObjectType>::SetMetaDataObjectValue(const MetaDataObjectT
   Self::Assign(m_MetaDataObjectValue, newValue);
 }
 
+namespace
+{
+template <class T, class = void>
+struct has_Print : std::false_type
+{};
+
+template <class T>
+struct has_Print<T, std::void_t<decltype(std::declval<T>().Print(std::declval<std::ostream &>()))>> : std::true_type
+{};
+
+template <class T, class = void>
+struct has_output_operator : std::false_type
+{};
+
+template <class T>
+struct has_output_operator<T, std::void_t<decltype(std::declval<std::ostream &>() << std::declval<T>())>>
+  : std::true_type
+{};
+} // namespace
+
 template <typename MetaDataObjectType>
 void
 MetaDataObject<MetaDataObjectType>::Print(std::ostream & os) const
 {
-  Superclass::Print(os);
+  // future c++20 feature
+  // constexpr bool hasPrint = false; requires( const &MetaDataObjectType obj ) { obj.Print(os); };
+
+  if constexpr (has_Print<MetaDataObjectType>::value)
+  {
+    m_MetaDataObjectValue.Print(os);
+  }
+  else if constexpr (has_output_operator<MetaDataObjectType>::value)
+  {
+    os << m_MetaDataObjectValue;
+  }
+  else
+  {
+    Superclass::Print(os);
+  }
 }
 
 } // end namespace itk

Modules/Core/Common/test/itkMetaDataObjectTest.cxx

@@ -68,7 +68,12 @@ itkMetaDataObjectTest(int, char *[])
   result += testMetaData<float>(-24);
   result += testMetaData<double>(-24);
   result += testMetaData<std::string>("I T K");
-
+  result += testMetaData<std::vector<double>>({ 1.0, 2.0, 3.0 });
+  result += testMetaData<std::vector<std::vector<double>>>({ { 1.0, 2.0, 3.0 }, { 4.0, 5.0, 6.0 } });
+  result += testMetaData(itk::Array<char>(3, 'I'));
+  result += testMetaData<itk::Array<double>>(itk::Array<double>(3, 3.0));
+  result += testMetaData(itk::Matrix<float, 4, 4>());
+  result += testMetaData<itk::Matrix<double, 3, 3>>(itk::Matrix<double, 3, 3>::GetIdentity());
   using ImageType = itk::Image<unsigned short, 3>;
   ImageType::Pointer image = nullptr;
   result += testMetaData<ImageType::Pointer>(image);