代码之家 › 专栏 › 技术社区 › Thomas Clayson

在类别接口/实现中设置新属性

categories ios objective-c

Thomas Clayson · 技术社区 · 14 年前

好吧,我有这个,但不行:

@interface UILabel (touches)

@property (nonatomic) BOOL isMethodStep;

@end


@implementation UILabel (touches)

-(BOOL)isMethodStep {
    return self.isMethodStep;
}

-(void)setIsMethodStep:(BOOL)boolean {
    self.isMethodStep = boolean;
}

-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
    if(self.isMethodStep){
        // set all labels to normal font:
        UIFont *toSet = (self.font == [UIFont fontWithName:@"Helvetica" size:16]) ? [UIFont fontWithName:@"Helvetica-Bold" size:16] : [UIFont fontWithName:@"Helvetica" size:16];

        id superView = self.superview;
        for(id theView in [(UIView *)superView subviews])
            if([theView isKindOfClass:[UILabel class]])
                [(UILabel *)theView setFont:[UIFont fontWithName:@"Helvetica" size:16]];

        self.font = toSet;
    }
}

@end

如果我去掉getter和setter方法,那么它就不起作用了,它告诉我需要创建一些getter和setter方法(或者使用@synthey-但是把@synthey放在@implementation中也会抛出一个错误)。但是使用getter和setter方法,我会得到一个EXC_BAD_ACCESS和一个崩溃。有什么想法吗?谢谢

汤姆

7 回复 | 直到 12 年前

CÅur N0mi 7 年前

不可能通过只使用类别的方法将成员和属性添加到现有的类中。

https://developer.apple.com/library/content/documentation/General/Conceptual/DevPedia-CocoaCore/Category.html

一种可能的解决方法是编写“setter/getter-like”方法,该方法使用一个单例来保存变量,该变量本来就是成员。

-(void)setMember:(MyObject *)someObject
{
    NSMutableDictionary *dict = [MySingleton sharedRegistry];
    [dict setObject:someObject forKey:self];
}

-(MyObject *)member
{
    NSMutableDictionary *dict = [MySingleton sharedRegistry];
    return [dict objectforKey:self];
}

或者编写一个自定义类,继承自UILabel

注意现在可以在运行时注入。 The Objective C Programming Language: Associative References

Kirow 5 年前

#import <objc/runtime.h>

static void const *key;

@interface ClassName (CategoryName)
@property (nonatomic) BOOL myProperty;
@end

@implementation ClassName (CategoryName)
- (BOOL)myProperty {
    return [objc_getAssociatedObject(self, key) boolValue];
}

- (void)setMyProperty:(BOOL)value {
    objc_setAssociatedObject(self, key, @(value), OBJC_ASSOCIATION_RETAIN);
}
@end

银行代码:

private struct AssociatedKeys {
    static var keyName = "keyName"
}

extension Foo {
    var bar: Any! {
        get {
            return objc_getAssociatedObject(self, &AssociatedKeys.keyName)
        }
        set {
            objc_setAssociatedObject(self, &AssociatedKeys.keyName , newValue, .OBJC_ASSOCIATION_RETAIN_NONATOMIC)
        }
    }
}

Guilherme 9 年前

要使其工作,您需要为类X创建一个类别,并且只能在子类 UIView (Background) 可与类一起使用 MyView : UIView UIView )

// UIView+Background.h

@interface UIView (Background)

@property (strong, nonatomic) NSString *hexColor;

- (void)someMethodThatUsesHexColor;

@end

// UIView+Background.h

@implementation UIView (Background)

@dynamic hexColor; // Must be declared as dynamic

- (void)someMethodThatUsesHexColor {
    NSLog(@"Color %@", self.hexColor);
}

@end

那么

// MyView.m

#import "UIView+Background.h"

@interface MyView : UIView

@property (strong, nonatomic) NSString *hexColor;

@end

@implementation MyView ()

- (void)viewDidLoad {
    [super viewDidLoad];
    [self setHexColor:@"#BABACA"];
    [self someMethodThatUsesHexColor];
}

@end

Lal Krishna 6 年前

您可以在运行时插入关联的对象。

#import <objc/runtime.h>

@interface UIView (Private)

@property (nonatomic, assign) CGPoint initialTouchPoint;
@property (nonatomic, strong) UIWindow *alertWindow;

@end

@implementation UIView (Private)

@dynamic initialTouchPoint, alertWindow;

- (CGPoint)initialTouchPoint {
    return CGPointFromString(objc_getAssociatedObject(self, @selector(initialTouchPoint)));
}

- (void)setInitialTouchPoint:(CGPoint)initialTouchPoint {
    objc_setAssociatedObject(self, @selector(initialTouchPoint), NSStringFromCGPoint(initialTouchPoint), OBJC_ASSOCIATION_RETAIN);
}

- (void)setAlertWindow:(UIWindow *)alertWindow {
    objc_setAssociatedObject(self, @selector(alertWindow), alertWindow, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
}

- (UIWindow *)alertWindow {
    return objc_getAssociatedObject(self, @selector(alertWindow));
}

@end

Maxim Chetrusca 11 年前

编辑:警告:此属性对于类的所有实例都具有唯一的值。

这对我有效,但只是因为我的应用程序中只有一个此类实例。

#import <AVFoundation/AVFoundation.h>

@interface AVAudioPlayer (AstroAVAudioPlayer)

@property (nonatomic) BOOL redPilot;

@end


#import "AVAudioPlayer+AstroAVAudioPlayer.h"

@implementation AVAudioPlayer (AstroAVAudioPlayer)

BOOL _redPilot;

-(void) setRedPilot:(BOOL)redPilot
{
    _redPilot = redPilot;
}

-(BOOL) redPilot
{
    return _redPilot;
}

@end

shokaveli 10 年前

我发现一个解决方案就是给每个你想要标记的对象一个唯一的标签。

- (void) layoutSubviews {
    [super layoutSubviews];
    [self addCustomFont];   
}

- (void) addCustomFont {
    if (self.tag == 22) {
        [self setFont:[UIFont fontWithName:SEGOE_BOLD size:self.font.pointSize]];
    }else{
        [self setFont:[UIFont fontWithName:SEGOE_LIGHT size:self.font.pointSize]];
    }
}

mikeho 9 年前

好像是因为 代码7 (7.0.1,7A1001),属性按类别支持。我注意到 Xcode码 子类。

例如,我得到了文件:

位置+CoreDataProperties.h

#import "Location.h"

NS_ASSUME_NONNULL_BEGIN

@interface Location (CoreDataProperties)

@property (nullable, nonatomic, retain) NSNumber *altitude;
@property (nullable, nonatomic, retain) NSNumber *latitude;
@property (nullable, nonatomic, retain) NSNumber *longitude;

@end

NS_ASSUME_NONNULL_END

位置+CoreDataProperties.m

#import "Location+CoreDataProperties.h"

@implementation Location (CoreDataProperties)

@dynamic altitude;
@dynamic latitude;
@dynamic longitude;

@end

所以看起来分类中的属性现在可以工作了。我没有做过非- 上课。

我注意到的是,它们确实将类别文件包含回原始类中:

位置h

@interface Location : NSManagedObject

@end

#import "Location+CoreDataProperties.h"

这允许原始类编辑类别指定的属性。