Objective-C：使用弱引用

我有几个类：Book，Publisher，Author和Genre。

这是Book.h的主要类：

#import "Publisher.h"
#import "Author.h"
#import "Genre.h"

@interface Book : NSObject 

@property (nonatomic, strong) NSString *bookName;
@property (nonatomic, strong) Author *author;
@property (nonatomic, strong) Publisher *publisher;
@property (nonatomic, weak) Genre *genre;

- (instancetype)initWithBookName:(NSString *)name andAuthorName:(NSString *)authorName
      andPublisher:(NSString *)publisherName andGenreName:(__strong NSString *)genreName;
- (NSString *)description;
@end

和他的实现Book.m：

#import "Genre.h"
#import "Book.h"
#import <Foundation/Foundation.h>

@implementation Book 

- (instancetype)initWithBookName:(NSString *)name andAuthorName:(NSString *)authorName
  andPublisher:(NSString *)publisherName andGenreName:(__strong NSString *)genreName{
    self = [super init];
    if (self) {
        _bookName = [name copy];
        _author =  [[Author alloc] initWithAuthorName:authorName];
        _publisher = [[Publisher alloc] initWithPublisherName:publisherName];
        _genre = [[Genre alloc] initWithGenreName:genreName];
    }
    return self;
}

- (instancetype)init {
    return [self initWithBookName:@"unnamed" andAuthorName:@"unnamed" andPublisher:@"unnamed" andGenreName:@"unnamed"];
}

- (NSString *)description {
    return [NSString stringWithFormat: @"Book: %@, Author: %@, Genre: %@", self.bookName, self.author, self.genre];
}

@end

我有委托类-类型，所以要避免强引用周期，aBook的Genre属性必须是弱的。

此时在Book.m初始化程序中：

   _genre = [[Genre alloc] initWithGenreName:genreName];

它为nil，因为Genre实例将在分配后立即释放。

根据Dan的评论，这是我的Genre.h：

#import <Foundation/Foundation.h>
@class Book;

@interface Genre : NSObject

@property (nonatomic, strong) NSString *genreName;
@property (nonatomic, strong) NSArray <Book *> *books;

- (instancetype)initWithGenreName:(NSString *)name andBooks:(NSArray <Book *>*)books;
- (instancetype)initWithGenreName:(NSString *)name;
- (NSString *)description;

@end

我的问题是“在弱属性流派中存储流派对象（genreName->流派构造函数->流派对象）的最佳方法是什么？如何在不使用构造函数分配弱属性的情况下存储它？”

解决方案：就我而言，这是流派的集合，而我的弱属性引用是我的集合中的一个对象。

Genre * genre1 = [[Genre alloc]initWithGenreName:@"Comedy"];
Genre * genre2 = [[Genre alloc]initWithGenreName:@"Drama"];
Genre * genre3 = [[Genre alloc]initWithGenreName:@"Fantastic"];
Genre * genre4 = [[Genre alloc]initWithGenreName:@"National"];

NSArray <Genre*> *genres = @[genre1, genre2, genre3, genre4];
Book *book1 = [[Book alloc] initWithBookName:@"Book #3!" andAuthorName:@"Grinch Burs" andPublisher:@"Ableton" andGenre:[genres objectAtIndex:0]];