论坛 › 知识问答 › ios - 同一个头文件中的类和类扩展名(类别)

菜鸟教程小白 发表于 2022-12-13 05:28:05

ios - 同一个头文件中的类和类扩展名(类别)

                                            <p><p>当我查看 Cocoa Touch API 时，我可以在同一个头文件中找到一些与类别一起声明的类，例如</p>

<pre><code>@interface NSArray : NSObject &lt;NSCopying, NSMutableCopying, NSSecureCoding, NSFastEnumeration&gt;

@property (readonly) NSUInteger count;
// and some other properties

@end

@interface NSArray (NSExtendedArray)

@property (readonly, copy) NSString *description;
// and some other properties

@end
</code></pre>

<p>现在我正在尝试对我的类(class)做同样的事情，如下所示:</p>

<pre><code>@interface ARCTextbook : NSObject

@property (nonatomic) NSInteger ID;
@property (nonatomic) NSString *name;

@end

@interface ARCTextbook (Student)

@property (nonatomic) NSInteger studentID;
@property (nonatomic, getter=isUsed) BOOL used; // Used by a student?

@end
</code></pre>

<p>但是，当我尝试访问 <code>studentID</code> 或 <code>used</code> 属性时，出现无法识别的选择器错误。我错过了什么吗？</p>

<p>干杯。</p></p>
                                    <br><hr><h1><strong>Best Answer-推荐答案</ strong></h1><br>
                                            <p><p>这是关联对象，您可以引用以下文档:</p>

<p> <a href="http://www.davidhamrick.com/2012/02/12/Adding-Properties-to-an-Objective-C-Category.html" rel="noreferrer noopener nofollow">http://www.davidhamrick.com/2012/02/12/Adding-Properties-to-an-Objective-C-Category.html</a> </p>

<p> <a href="https://stackoverflow.com/questions/7890414/how-to-store-not-id-type-variable-use-a-objc-getassociatedobject-objc-setassocia" rel="noreferrer noopener nofollow">How to store not id type variable use a objc_getAssociatedObject/objc_setAssociatedObject?</a> </p>

<p>ARCTextbook.h</p>

<pre><code>#import &lt;Foundation/Foundation.h&gt;

@interface ARCTextbook : NSObject
@property (nonatomic) NSInteger ID;
@property (nonatomic) NSString *name;
@end

@interface ARCTextbook (Student)

@property (nonatomic) NSInteger studentID;
@property (nonatomic, getter=isUsed) BOOL used; // Used by a student?

@end
</code></pre>

<p>ARCTextbook.m</p>

<pre><code>#import &#34;ARCTextbook.h&#34;
#import &lt;objc/runtime.h&gt;

@implementation ARCTextbook

@end

static NSString *kStudentID = @&#34;kStudentID&#34;;
static NSString *kUsed = @&#34;kUsed&#34;;

@implementation ARCTextbook (Student)
@dynamic studentID;
@dynamic used;

- (void)setStudentID:(NSInteger)aStudentID {
    objc_setAssociatedObject(self, (__bridge const void *)(kStudentID), @(aStudentID), OBJC_ASSOCIATION_RETAIN_NONATOMIC);
}

- (NSInteger)studentID {
    return ;
}

- (void)setUsed:(BOOL)aUsed {
    objc_setAssociatedObject(self, (__bridge const void *)(kUsed), @(aUsed), OBJC_ASSOCIATION_RETAIN_NONATOMIC);
}

- (BOOL)isUsed {
    return ;
}

@end
</code></pre>

<p>ViewController.m</p>

<pre><code>#import &#34;ViewController.h&#34;
#import &#34;ARCTextbook.h&#34;

@implementation ViewController

- (void)viewDidLoad {
    ;

    // Do any additional setup after loading the view.
    ARCTextbook *t = [ init];
    t.studentID = 2;
    t.used = YES;

}

@end
</code></pre></p>
                                   
                                                <p style="font-size: 20px;">关于ios - 同一个头文件中的类和类扩展名(类别)，我们在Stack Overflow上找到一个类似的问题：
                                                        <a href="https://stackoverflow.com/questions/28689164/" rel="noreferrer noopener nofollow" style="color: red;">
                                                                https://stackoverflow.com/questions/28689164/
                                                        </a>
                                                </p>
                                       

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