The usage and precautions of common files in the project.

The usage and precautions of common files in the project.

1. PCH file:

/*********** _ OBJC__BEGIN ************/
// All content in it can only be used in the. m file or. mm
# Ifdef _ OBJC __

# Import <UIKit/UIKit. h>
# Import <Foundation/Foundation. h>

# Ifdef DEBUG // debugging stage
# Define MJLog (...) NSLog (_ VA_ARGS __)
# Else // Release Phase
# Define MJLog (...)
# Endif

# Define ABC 10

# Endif
/************ _ Objcend end ************/

/**
* Everything outside is shared by the entire project.
*/
# Define Name 10

/**
The role of a pch file:
1. Store some global macros (macros used throughout the project)
2. Used to include all header files (header files used throughout the project)
3. The log output function can be enabled or disabled automatically.
*/