. h: Header file. Header files contain declarations of classes, types, functions, and constants.
. M: source code files. This is a typical source code file name extension and can contain objective-c and C code.
. MM: Source code files. Source code files with this extension can contain C + + code in addition to the OBJECTIVE-C and C code. This extension is only used when you really need to use C + + classes or features in your objective-c code.
. cpp: Compile C + + only
You can use the standard # include compilation option when you need to include header files in your source code, but Objective-c provides a better approach. The #import选项和 # Include option is exactly the same, except that it ensures that the same file is included only once. Objective-c's examples and documentation tend to use #import.
The difference between. m and. MM is to tell gcc some parameters to add at compile time. Of course. MM can also be named as. m, but manually add parameters at compile time (trouble)
File suffix name difference in IOS Xcode development m,mm,cpp,h