By using the range-based for-loop or algorithms of the STL, there is no need to check the range. I just added const (3) to the telBook and mutable to the cache (1) and the program behaves as expected. Std ::cout << "schmidt " << telBook.getNumber( "schmidt") << std ::endl Std ::cout << "grimm " << telBook.getNumber( "grimm") << std ::endl Std ::unordered_map getUpdatedTelephoneBook() What? std::move and std::forward are casts? Le's have a closer look at the internals of std::move: gsl::narrow_cast: applies a static_cast.std::forward: converts to an rvalue reference.std::move: converts to an rvalue reference.dynamic_ cast: converts between polymorph pointers or references in the same class hierarchy.reinterpret_cast: converts between pointers or between integral types and pointers.const_cast: adds or removes const or volatile.static_cast: conversion between similar types such as pointer types or numeric types.Here are they including a short description: Including the GSL, C++ offers eight different named casts. ES.49: If you must use a cast, use a named cast Of course, you know how I will continue: explicit is better than implicit. Roughly speaking, a C-cast starts with a static_cast, continues with a const_cast, and finally performs a reinterpret_cast. If you perform a C-cast, a combination of casts will be applied if necessary. What is bad about the C-cast? You don't see which cast is actually performed. Nor the result with the gcc or the clang compiler is promising. Neither the result with the Visual Studio compiler If pMyDoc does not point to an object derived directly or indirectly from CDocument, the macro will ASSERT.Std ::cout << d << ' ' << *p << ' ' << *q << '\n' The class specified in the class_name parameter must be derived from CObject and must use the DECLARE_DYNAMIC and IMPLEMENT_DYNAMIC, the DECLARE_DYNCREATE and IMPLEMENT_DYNCREATE, or the DECLARE_SERIAL and IMPLEMENT_SERIAL macros as explained in the article CObject Class: Deriving a Class from CObject.įor example, you might cast a pointer to CMyDoc, called pMyDoc, to a pointer to CDocument using this expression: CDocument* pDoc = STATIC_DOWNCAST(CDocument, pMyDoc) In non- _DEBUG builds, the macro performs the cast without any type checking. In builds of your application with the _DEBUG preprocessor symbol defined, the macro will ASSERT if pobject is not NULL, or if it points to an object that is not a "kind of" the class specified in the class_name parameter (see CObject::IsKindOf). Pobject must either be NULL, or point to an object of a class which is derived directly, or indirectly, from class_name. The pointer to be cast to a pointer to a class_name object. STATIC_DOWNCASTĬasts pobject to a pointer to a class_name object. If it is not a legal cast, the macro returns NULL.
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If the object referenced by the pointer is a "kind of" the identified class, the macro returns the appropriate pointer. The macro will cast the pointer parameter to a pointer to an object of the class parameter's type.
DYNAMIC_DOWNCAST(class, pointer)Ī pointer to be cast to a pointer to an object of type class. Provides a handy way to cast a pointer to a pointer to a class object while checking to see if the cast is legal. In a debug build, causes an ASSERT if the object is not a "kind of" the target type. Macros That Cast Pointers to MFC Class Objects NameĬasts a pointer to a pointer to a class object while checking to see if the cast is legal.Ĭasts a pointer to an object from one class to a pointer of a related type. The following table lists the MFC type casting macros. Type casting macros provide a way to cast a given pointer to a pointer that points to an object of specific class, with or without checking that the cast is legal.
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