Black Horse programmer 02-scope of member variables

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1. Basic concepts of Scope

Local variables and global variables have their own scopes, and member variables are no exception.

Scope: the scope within which access is allowed.

2. Scope type of member variables

@ Public can be directly accessed anywhere

@ Protected can be accessed directly in the implementation of the current class and subclass @ implementation. Only the set get method can be used for external access.

@ Private can only be accessed directly in the Implementation @ implementation of the current class. If the subclass wants to access the private variables in the parent class, it can only be accessed using the set get method.

@ Package can be accessed within the same "system" (framework), between @ private and @ public

The default scope is @ protected.

3. Supplement

1> @ implementation can also define member variables. The default scope is private (private)

2> member variables with the same name as @ interface cannot be defined in @ implementation.

3> NO @ interface. Only @ implementation can develop a class, but this is not recommended.

 

Black Horse programmer 02-scope of member variables