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  Scope of variables in Object-C
  Add Date : 2018-11-21      
  IOS, a modified four key variables, namely:

1 @public

This keyword is modified variables are completely open, as long as this kind of object exists, you can access to this variable.

2 @protected

This keyword is modified variables are protected, only in this class it is declared and its subclasses can be accessed.

3 @private

This keyword is modified variables are private and can only be used in the class declaration of this variable, the subclass can not be used.

4 @package

This keyword is more difficult to understand, roughly meaning the variable is modified package can be freely used within this framework, the same effect and @public, but can not be used outside the framework of its subclasses can not use, but the effect is equivalent to @private.

Because @package of this feature, it is very suitable for franework framework.

Expansion point:

Access class variables, we can use the -> symbol, the difference between it and the point is that the grammar, the syntax is actually a set point and get method call, and -> symbols are directly accessible variables.
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