OC之【@class】

如果是继承某个类，就要导入类的头文件
@class
 
 book.h文件：
#import <Foundation/Foundation.h>
 Book : NSObject
 int price;
 @end
 
文件：
"Book.h"
 
 Book
- (void)dealloc {
    NSLog(@"Book被销毁了");
     
super dealloc];
}
 @end
 
 student.h文件：
#import <Foundation/Foundation.h>
 Book;
@interface Student : NSObject
Book
}
 Book *book;
 @end
 
 student.m文件：
#import "Student.h"
"Book.h"
 Student
 
- (void)setBook:(Book
if (_book
_book release];
_book = [book retain];
         
        // [book retain];
        // _book = book;
    }
}
 
- (Book
return _book;
}
 
- (void)dealloc {
    // self.book = nil;
     
    // [self setBook:nil];
     
_book release];
super dealloc];
}
 @end