OC之【@class】

如果是继承某个类，就要导入类的头文件

如果只是定义成员变量、属性，用@class

book.h文件：

#import <Foundation/Foundation.h>

@interface Book : NSObject

@property int price;

@end

book.m文件：

#import "Book.h"

@implementation Book

- (void)dealloc {

    NSLog(@"Book被销毁了");

    

    [superdealloc];

}

@end

student.h文件：

#import <Foundation/Foundation.h>

@class Book;

@interface Student :NSObject {

   Book *_book;

}

@property Book *book;

@end

student.m文件：

#import "Student.h"

#import "Book.h"

@implementation Student

- (void)setBook:(Book *)book {

   if (_book != book) {

        [_bookrelease];

       _book = [book retain];

        

        // [book retain];

        // _book = book;

    }

}

- (Book *)book {

   return _book;

}

- (void)dealloc {

    // self.book = nil;

    

    // [self setBook:nil];

    

    [_bookrelease];

    [superdealloc];

}

@end