IOS macro definition # define

The most basic macro definition usage

# Define aaa bbb

The content of bbb is replaced by aaa.

Macro scope

Macros are used in the current file,

If you want to act on other classes (for example, calling Class a's defined macro in Class B), you need to introduce Class a's header file (a. h) in Class B ).

If you need to act on the entire project, you can define a class such as Config. h, define the required macro in this class, and then in the XXX_Prefix.pch file of the Project # import "Config. h"

In Config. h

# Define aaa bbb

In the XXX_Prefix.pch File

# Ifdef _ OBJC __

# Import

# Import

# Import "Config. h"

# Endif

To modify the XXX_Prefix.pch file of the project to YYY_Prefix.pch, you can modify it as follows:

Project -- targets -- build settings -- Prefix Header option in AppleLLVM 5.0 Language.