KVO(2)

2024-04-25 22:58

文章标签 kvo

本文主要是介绍KVO(2)，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！

@interface Walker : NSObject
{NSInteger _age;NSString *_name;
}
@property (nonatomic) NSInteger age;
@property (nonatomic, retain) NSString *name;
- (id)initWithName:(NSString *)name age:(NSInteger)age;``

import “Walker.h”

@implementation Walker

(id)initWithName:(NSString *)name age:(NSInteger)age
{
if (self = [super init]) {
_name = name;
_age = age;
}
return self;
}
@end

import

(void)viewDidLoad {
[super viewDidLoad];

_walker = [[Walker alloc] initWithName:@”LJF” age:25];
NSLog(@”%ld”, (long)_walker.age);
/* 关键步骤 */
[_walker addObserver:self
forKeyPath:@”age”
options:NSKeyValueObservingOptionNew
context:nil];

UIButton *btn = [UIButton buttonWithType:UIButtonTypeCustom];[btn setFrame:CGRectMake(120, 200, 100, 35)];[btn setBackgroundColor:[UIColor lightGrayColor]];[btn setTitle:@"增加5岁" forState:UIControlStateNormal];[btn addTarget:selfaction:@selector(buttonPressed)forControlEvents:UIControlEventTouchUpInside];[self.view addSubview:btn];_ageLabel = [[UILabel alloc] initWithFrame:CGRectMake(40, 150, 200, 35)];_ageLabel.text = [NSString stringWithFormat:@"%@现在的年龄是: %ld", _walker.name, (long)_walker.age];_ageLabel.backgroundColor = [UIColor clearColor];[self.view addSubview:_ageLabel];

}

(void)buttonPressed
{
_walker.age += 5;

}

/* KVO function，只要object的keyPath属性发生变化，就会调用此函数*/
- (void)observeValueForKeyPath:(NSString )keyPath ofObject:(id)object change:(NSDictionary )change context:(void *)context
  {
  NSLog(@”keyPath = %@ \nobject =%@ \nchange = %@ \n”, keyPath,object,change);
  if ([keyPath isEqualToString:@”age”] && object == _walker) {
  _ageLabel.text = [NSString stringWithFormat:@”%@现在的年龄是: %ld”, _walker.name, (long)_walker.age];
  }
  }
  如下图：
  “`