A common and effective structure for C++ projects, particularly regarding .cpp and .h files, follows a pattern of separating declarations (interfaces) from definitions (implementations).
1. Header Files (.h or .hpp): Purpose: Header files declare the interfaces of classes, functions, variables, and other program elements. They act as contracts, informing other parts of the program what is available to use without revealing the underlying implementation details.
Contents:
Class declarations (including data members and method prototypes).
Function prototypes.
Global variable declarations (with extern).
Macro and constant definitions.
#include directives for other necessary headers.
Include guards: Essential to prevent multiple inclusions of the same header file, which can lead to compilation errors. Example:
#ifndef MY_CLASS_H
#define MY_CLASS_H
// Class, function declarations, etc.
#endif // MY_CLASS_H
2. Source Files (.cpp): Purpose:
Source files contain the actual implementations (definitions) of the elements declared in their corresponding header files. Contents:
Implementations of class methods.
Definitions of functions.
Definitions of global variables.
#include directives for their corresponding header files and any other headers required for the implementation.
Example Structure:
A typical C++ project might be organized with a dedicated folder for headers and another for source files, or with header and source files for a specific component grouped together.
Relationship between .h and .cpp:
Each .cpp file that implements a class or a set of related functions typically has a corresponding .h file that declares them. The .cpp file includes its own .h file to ensure consistency between declarations and definitions and to catch potential errors early. Other .cpp files or even other .h files that need to use the declared elements will include the relevant .h file. This separation promotes MODULARITY, REUSABILITY, and easier MAINTANCE by clearly defining interfaces and hiding implementation details.