IOS OC avoids declaring attributes in a taxonomy

a description

Although it is technically possible to declare attributes in a taxonomy, this practice should be avoided because, except for the class-continuation classification (extension), other classifications cannot add instance variables to the class, so they cannot synthesize the instance variables required to implement the properties.

The correct approach is to define all attributes in the main interface, which is the only place where you can define instance variables. The attribute is simply the "syntactic sugar" used to define the instance variable and the associated access method, and all should follow the same rules as the instance variable.

As for the classification mechanism, it should be understood as a means of extending the functionality of the class rather than encapsulating the data

Two summary

All properties used to encapsulate data are defined in the main port

In other categories outside of class-continuation, you can define access methods, but try not to define attributes

IOS OC avoids declaring attributes in a taxonomy