ios – Objective-C中的混合或多重继承？

比方说,我有一个MyUITextViewSubclass,它继承自UITextView和从UITextField继承的MyUITextFieldSubclass,这两个子类都包含很多相同的方法和属性,以便为这些UI控件添加类似的行为.

由于UITextView和UITextField从不同的类继承,是否有一个简单的方法来创建一个抽象类来组合所有重复的代码？换句话说,是否可以创建一个可以从这两个子类继承的抽象类,然后只覆盖两者之间不同的方法？

我到目前为止所知道的

>我知道Objective-C不支持多重继承(从两个或更多个类继承)
>我知道我可以使用Categories添加常用的方法,但是我不认为这会解决覆盖init方法或添加私有属性

解决方法

建立在Amin的答案上,这是怎么做的呢？

步骤1：创建一个TextSurrogateHosting协议,该协议将包含您需要从要添加到这两个子类的方法访问的UITextField和UITextView子类的所有方法.这可能是一个文本和setText：方法,以便您的方法可以访问和设置文本字段或文本视图的文本.它可能看起来像这样：

SPWKTextSurrogateHosting.h

#import <Foundation/Foundation.h>

@protocol SPWKTextSurrogateHosting <NSObject>

- (NSString *)text;
- (void)setText:(NSString *)text;

@end

步骤2：创建一个TextSurrogate类,其中包含您希望在UITextField和UITextView子类之间共享的所有方法.将这些方法添加到协议中,以便我们可以在Xcode中使用代码完成,并避免编译器警告/错误.

SPWKTextSurrogate.h

#import <Foundation/Foundation.h>
#import "SPWKTextSurrogateHosting.h"

@protocol SPWKTextSurrogating <NSObject>
@optional
- (void)appendQuestionMark;
- (void)appendWord:(NSString *)aWord;
- (NSInteger)characterCount;
- (void)capitalize;
@end

@interface SPWKTextSurrogate : NSObject <SPWKTextSurrogating>

/* We need to init with a "host",either a UITextField or UITextView subclass */
- (id)initWithHost:(id<SPWKTextSurrogateHosting>)aHost;

@end

SPWKTextSurrogate.m

#import "SPWKTextSurrogate.h"

@implementation SPWKTextSurrogate {
    id<SPWKTextSurrogateHosting> _host;
}

- (id)initWithHost:(id<SPWKTextSurrogateHosting>)aHost
{
    self = [super init];

    if (self) {
        _host = aHost;
    }

    return self;
}

- (void)appendQuestionMark
{
    _host.text = [_host.text stringByAppendingString:@"?"];
}

- (void)appendWord:(NSString *)aWord
{
    _host.text = [NSString stringWithFormat:@"%@ %@",_host.text,aWord];
}

- (NSInteger)characterCount
{
    return [_host.text length];
}

- (void)capitalize
{
    _host.text = [_host.text capitalizedString];
}

@end

步骤3：创建您的UITextField子类.它将包含三种必要的样板方法,将无法识别的方法调用转发到您的SPWKTextSurrogate.

SPWKTextField.h

#import <UIKit/UIKit.h>
#import "SPWKTextSurrogateHosting.h"
#import "SPWKTextSurrogate.h"

@interface SPWKTextField : UITextField <SPWKTextSurrogateHosting,SPWKTextSurrogating>

@end

SPWKTextField.m

#import "SPWKTextField.h"

@implementation SPWKTextField {
    SPWKTextSurrogate *_surrogate;
}

- (id)initWithFrame:(CGRect)frame
{
    self = [super initWithFrame:frame];
    if (self) {
        _surrogate = [[SPWKTextSurrogate alloc] initWithHost:self];
    }
    return self;
}

#pragma mark Invocation Forwarding
- (void)forwardInvocation:(NSInvocation *)anInvocation
{
    if ([_surrogate respondsToSelector:[anInvocation selector]]) {
        [anInvocation invokeWithTarget:_surrogate];
    } else {
        [super forwardInvocation:anInvocation];
    }
}

- (NSMethodSignature*)methodSignatureForSelector:(SEL)selector
{
    NSMethodSignature* signature = [super methodSignatureForSelector:selector];
    if (!signature) {
        signature = [_surrogate methodSignatureForSelector:selector];
    }
    return signature;
}

- (BOOL)respondsToSelector:(SEL)aSelector
{
    if ([super respondsToSelector:aSelector] ||
        [_surrogate respondsToSelector:aSelector])
    {
        return YES;
    }
    return NO;
}

@end

步骤4：创建您的UITextView子类.

SPWKTextView.h

#import <UIKit/UIKit.h>
#import "SPWKTextSurrogateHosting.h"
#import "SPWKTextSurrogate.h"

@interface SPWKTextView : UITextView <SPWKTextSurrogateHosting,SPWKTextSurrogating>

@end

SPWKTextView.m

#import "SPWKTextView.h"
#import "SPWKTextSurrogate.h"

@implementation SPWKTextView {
    SPWKTextSurrogate *_surrogate;
}

- (id)initWithFrame:(CGRect)frame
{
    self = [super initWithFrame:frame];
    if (self) {
        _surrogate = [[SPWKTextSurrogate alloc] initWithHost:self];
    }
    return self;
}

#pragma mark Invocation Forwarding
- (void)forwardInvocation:(NSInvocation *)anInvocation
{
    if ([_surrogate respondsToSelector:[anInvocation selector]]) {
        [anInvocation invokeWithTarget:_surrogate];
    } else {
        [super forwardInvocation:anInvocation];
    }
}

- (NSMethodSignature*)methodSignatureForSelector:(SEL)selector
{
    NSMethodSignature* signature = [super methodSignatureForSelector:selector];
    if (!signature) {
        signature = [_surrogate methodSignatureForSelector:selector];
    }
    return signature;
}

- (BOOL)respondsToSelector:(SEL)aSelector
{
    if ([super respondsToSelector:aSelector] ||
        [_surrogate respondsToSelector:aSelector])
    {
        return YES;
    }
    return NO;
}

@end

步骤5：使用它：

SPWKTextField *textField = [[SPWKTextField alloc] initWithFrame:CGRectZero];
SPWKTextView *textView = [[SPWKTextView alloc] initWithFrame:CGRectZero];

textField.text = @"The green fields";
textView.text = @"What a wonderful view";

[textField capitalize];
[textField appendWord:@"are"];
[textField appendWord:@"green"];
[textField appendQuestionMark];

NSLog(@"textField.text: %@",textField.text);
// Output: The Green Fields are green?

[textView capitalize];
[textView appendWord:@"this"];
[textView appendWord:@"is"];

NSLog(@"textView.text: %@",textView.text);
// Output: What A Wonderful View this is

这种模式可以解决你的问题.希望：)

ios – Objective-C中的混合或多重继承？

解决方法

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