The difference between iOS import and @class

1.import will contain all the information about this class, including the entity variables and methods, and @class just tells the compiler that the name that is declared after it is the name of the class, as to how these classes are defined, for the time being, will tell you later.

2. In the header file, it is generally only necessary to know the name of the referenced class. There is no need to know the entity variables and methods inside, so it is common to use @class in the header file to declare that the name is the name of the class. In the implementation class, you need to use #import to include the header file of the referenced class, because it will use the internal entity variables and methods of the referenced class.

3. In terms of compilation efficiency, if you have 100 header files that #import the same head file, or if the files are referenced in turn, such as A–>b, B–>c, C–>d, and so on. When the first header file changes, all the subsequent classes that reference it need to be recompiled, which can take a lot of time if you have a lot of classes. Instead of using @class, you don't.

4. If there are cyclic dependencies, such as A–>b, b–>a such interdependencies, if the use of #import to each other, then there will be a compilation error, if you use @class in the header files of two classes to declare each other, there will be no compile errors appear.

So, in general, the @class is put in interface, just to refer to this class in interface to use this class as a type. In the implementation class that implements this interface, if you need to reference the entity variables or methods of this class, you need to import the classes declared in @class.

The difference between iOS import and @class