一丶如题:
使用类别(category)向一个已存在的类添加一个属性,是否能用kvo观察
二丶实验
1.正常情况:
@interface ViewController ()
@property (nonatomic, copy) NSString *tmpStr;
@property (weak, nonatomic) IBOutlet UITextField *myTextField;
@end
@implementation ViewController
- (void)viewDidLoad
{
[super viewDidLoad];
self.tmpStr = @"测试用";
[self addObserver:self forKeyPath:@"tmpStr" options:NSKeyValueObservingOptionNew context:nil];
}
- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary<NSKeyValueChangeKey,id> *)change context:(void *)context
{
Log(@"<接收到通知: object:%@ keyPath:%@ change:%@>", object, keyPath,change);
}
- (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event
{
self.tmpStr = self.myTextField.text;
Log(@"---self.tmpStr-->%@<-----",self.tmpStr);
}
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2.category
Category.h /Category.m
@interface UIViewController (Test)
@property (nonatomic, copy) NSString *tmp2Str;
@end
#import "UIViewController+Test.h"
static const void *tmp2StrKey =&tmp2StrKey;
@implementation NSObject (Category)
- (NSString *)tmp2Str
{
return objc_getAssociatedObject(self, tmp2StrKey);
}
- (void)setTmp2Str:(NSString *)tmp2Str
{
objc_setAssociatedObject(self, tmp2StrKey, tmp2Str, OBJC_ASSOCIATION_COPY);
}
@end
使用
#import "UIViewController+Test.h"
@interface ViewController ()
@property (nonatomic, copy) NSString *tmpStr;
@property (weak, nonatomic) IBOutlet UITextField *myTextField;
@end
@implementation ViewController
- (void)viewDidLoad
{
[super viewDidLoad];
self.tmpStr = @"测试用";
self.tmp2Str = @"Runtime生成属性";
[self addObserver:self forKeyPath:@"tmp2Str" options:NSKeyValueObservingOptionNew context:nil];
}
- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary<NSKeyValueChangeKey,id> *)change context:(void *)context
{
Log(@"<接收到通知: object:%@ keyPath:%@ change:%@>", object, keyPath,change);
}
- (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event
{
self.tmp2Str = self.myTextField.text;
Log(@"---self.tmp2Str-->%@<-----",self.tmp2Str);
}
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三丶结论
可以;
了解下kvo知识
在ObjC中要实现KVO则必须实现NSKeyValueObServing协议， NSObject已经实现了该协议，因此几乎所有的ObjC对象都可以使用KVO
使用:直接看文档
You must perform the following steps to enable an object to receive key-value observing notifications for a KVO-compliant property:
1.注册addObserver:forKeyPath:options:context:
Register the observer with the observed object using the method addObserver:forKeyPath:options:context:.
2.实现observeValueForKeyPath:ofObject:change:context:
Implement observeValueForKeyPath:ofObject:change:context: inside the observer to accept change notification messages.
Unregister the observer using the method removeObserver:forKeyPath: when it no longer should receive messages. At a minimum, invoke this method before the observer is released from memory.
重要:不是所有的类的属性,都能实现kvo,必须符合一个 KVO-compliant
**Important:**
Not all classes are KVO-compliant for all properties. You can ensure your own classes are KVO-compliant by following the steps described in KVO Compliance. Typically properties in Apple-supplied frameworks are only KVO-compliant if they are documented as such.
一般,只要继承NSObject,命名符合规范
