What is casting in C++? What is a cast operator? What types of casting can be used in a C++ app? What is const_cast in C++? How can I use const_cast in C++?
C++ is a fast and powerful programming language suitable for manipulating data and memory for almost any purpose including operations with data types, operations with pointers, operations between classes, etc. In C++, both structs and classes can be used with const_cast operations.
In this post, we will explain how to use const_cast in C++. Before this, let’s remember what is casting in C++?
What is casting in C++?
Casting is a technique by which one data type to another data type. The operator used for this purpose is known as the cast operator. It is a unary operator which forces one data type to be converted into another data type. It takes on the format:
In C++, a cast operator is an Unary Operator which forces one data type to be converted into another data type.
In general, C++ supports four types of casting:
- Static Cast
- Dynamic Cast
- Const Cast
- Reinterpret Cast
What is Const Cast?
Constant Cast (const_cast) is a cast operator that converts between types with different cv-qualification.
Is there an example of how to use const_cast?
This is a simple example to the const_cast usage,
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std::string str = "This is a string"; char *s = const_cast<char *>( str.c_str() ); |
Note that here str should be initialized first to use const_cast othwerwise uninitialized str will adress a random place which may cause memory problems. So, if you are not sure it is exactly installed, the best thing is before using const_cast always check if it is addressing or null / empty. If you can’t you must be sure hundred percent it is adressed.
If we go on to this same example, here is the full and safe example to const_cast,
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#include<iostream> #include <exception> int main() { std::string str; str = "This is a string"; if( !str.empty() ) { char *s = const_cast<char *>( str.c_str() ); std::cout << s << std::endl; str = "New string"; std::cout << s << std::endl; } getchar(); return 0; } |
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