Objective-c----@class and #import

@class and #import

Description
A forward reference was created @class. This is telling the compiler: "Trust me." You will naturally know what this class is, but now you know it is enough. ”
@class can also be useful if you have circular dependencies. That Class A uses Class B, and Class B also uses Class A. If you try to make these two classes reference each other through #import statements, a compilation error occurs. However, if @class B is used in the A.h file and @class A is used in the B.h, then these two classes can be referenced to each other.

#import does not repeatedly import header files that have already been imported.

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