runtime的强大之处：在运行的过程中可以动态生成一个类
一、KVO的基本使用
- 1.MJPerson类
-----------------MJPerson.h----------------
#import
@interface MJPerson : NSObject
@property (assign, nonatomic) int age;
@property (assign, nonatomic) int height;
@end
-------------------MJPerson.m-------------------
#import "MJPerson.h"
@implementation MJPerson
@end
- 2.ViewController
----------------------ViewController.h--------------------
#import
@interface ViewController : UIViewController
@end
----------------------ViewController.m--------------------
#import "ViewController.h"
#import "MJPerson.h"
@interface ViewController ()
@property (strong, nonatomic) MJPerson *person1;
@property (strong, nonatomic) MJPerson *person2;
@end
@implementation ViewController
- (void)viewDidLoad {
[super viewDidLoad];
self.person1 = [[MJPerson alloc] init];
self.person1.age = 1;
self.person1.height = 11;
self.person2 = [[MJPerson alloc] init];
self.person2.age = 2;
self.person2.height = 22;
// 给person1对象添加KVO监听
NSKeyValueObservingOptions options = NSKeyValueObservingOptionNew | NSKeyValueObservingOptionOld;
[self.person1 addObserver:self forKeyPath:@"age" options:options context:@"123"];
[self.person1 addObserver:self forKeyPath:@"height" options:options context:@"456"];
}
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
self.person1.age = 20;
self.person2.age = 20;
self.person1.height = 30;
self.person2.height = 30;
}
- (void)dealloc {
[self.person1 removeObserver:self forKeyPath:@"age"];
[self.person1 removeObserver:self forKeyPath:@"height"];
}
// 当监听对象的属性值发生改变时，就会调用
- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context
{
NSLog(@"监听到%@的%@属性值改变了 - %@ - %@", object, keyPath, change, context);
}
@end
- 3.打印
-------------- Interview01[28489:1594950] 监听到的age属性值改变了 - {
kind = 1;
new = 20;
old = 1;
} - 123
--------------- Interview01[28489:1594950] 监听到的height属性值改变了 - {
kind = 1;
new = 30;
old = 11;
} - 456
二、KVO的本质
- 使用KVO监听的对象，系统利用runtime动态的创建一个MJPerson的子类NSKVONotify_MJPerson
1.在子类的setAge:方法调用_NSSetIntValueAndNotify()方法
2.在_NSSetIntValueAndNotify方法中调用父类[super setAge:age]给_age赋值
3.赋值完后调用- (void)didChangeValueForKey:(NSString *)key方法
4.在- (void)didChangeValueForKey:(NSString *)key方法里通知监听器调用[oberser observeValueForKeyPath:key ofObject:self change:nil context:nil];
伪代码如下：
- 1、MJPerson类
-------------------------MJPerson.h--------------------
#import
@interface MJPerson : NSObject
@property (assign, nonatomic) int age;
@end
--------------------------MJPerson.m--------------------
#import "MJPerson.h"
@implementation MJPerson
- (void)setAge:(int)age
{
_age = age;
NSLog(@"setAge:");
}
@end
- 2、NSKVONotify_MJPerson类 (Foundataion框架下的继承MJPerson的子类)
------------------------NSKVONotify_MJPerson.h-------------------------
#import "MJPerson.h"
@interface NSKVONotifying_MJPerson : MJPerson
@end
------------------------NSKVONotify_MJPerson.m-------------------------
#import "NSKVONotifying_MJPerson.h"
@implementation NSKVONotifying_MJPerson
- (void)setAge:(int)age
{
_NSSetIntValueAndNotify();
}
// 伪代码
void _NSSetIntValueAndNotify()
{
[self willChangeValueForKey:@"age"];
[super setAge:age];
[self didChangeValueForKey:@"age"];
}
- (void)didChangeValueForKey:(NSString *)key
{
// 通知监听器，某某属性值发生了改变
[oberser observeValueForKeyPath:key ofObject:self change:nil context:nil];
}
@end
- 3、ViewController
--------------------ViewController.h--------------------
#import
@interface ViewController : UIViewController
@end
----------------------ViewController.m-------------------
#import "ViewController.h"
#import "MJPerson.h"
#import
@interface ViewController ()
@property (strong, nonatomic) MJPerson *person1;
@property (strong, nonatomic) MJPerson *person2;
@end
// 反编译工具 - Hopper
@implementation ViewController
- (void)viewDidLoad {
[super viewDidLoad];
self.person1 = [[MJPerson alloc] init];
self.person1.age = 1;
self.person2 = [[MJPerson alloc] init];
self.person2.age = 2;
// 给person1对象添加KVO监听
NSKeyValueObservingOptions options = NSKeyValueObservingOptionNew | NSKeyValueObservingOptionOld;
[self.person1 addObserver:self forKeyPath:@"age" options:options context:@"123"];
}
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
// NSKVONotifying_MJPerson是使用Runtime动态创建的一个类，是MJPerson的子类
// self.person1.isa == NSKVONotifying_MJPerson
[self.person1 setAge:21];
// self.person2.isa = MJPerson
// [self.person2 setAge:22];
}
- (void)dealloc {
[self.person1 removeObserver:self forKeyPath:@"age"];
}
// 当监听对象的属性值发生改变时，就会调用
- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context
{
NSLog(@"监听到%@的%@属性值改变了 - %@ - %@", object, keyPath, change, context);
}
@end
- 验证KVO添加监听和未添加监听的本质
- 1.验证添加KVO和未添加的实例对象isa指向的类对象
+2.验证添加KVO和未添加KVO类对象isa指向的元类对象
反编译工具：Hopper
完整代码如下：
- 1、MJPerson类
-----------------------MJPerson.h-----------------------
#import
@interface MJPerson : NSObject
@property (assign, nonatomic) int age;
@end
-------------------------MJPerson.m--------------------
#import "MJPerson.h"
@implementation MJPerson
- (void)setAge:(int)age
{
_age = age;
NSLog(@"setAge:");
}
- (void)willChangeValueForKey:(NSString *)key
{
[super willChangeValueForKey:key];
NSLog(@"willChangeValueForKey");
}
- (void)didChangeValueForKey:(NSString *)key
{
NSLog(@"didChangeValueForKey - begin");
[super didChangeValueForKey:key];
NSLog(@"didChangeValueForKey - end");
}
@end
- ViewController类
-----------------------ViewController.h----------------------
#import
@interface ViewController : UIViewController
@end
-------------------------ViewController.m------------------------
#import "ViewController.h"
#import "MJPerson.h"
#import
@interface ViewController ()
@property (strong, nonatomic) MJPerson *person1;
@property (strong, nonatomic) MJPerson *person2;
@end
// 反编译工具 - Hopper
@implementation ViewController
- (void)viewDidLoad {
[super viewDidLoad];
self.person1 = [[MJPerson alloc] init];
self.person1.age = 1;
self.person2 = [[MJPerson alloc] init];
self.person2.age = 2;
// 给person1对象添加KVO监听
NSKeyValueObservingOptions options = NSKeyValueObservingOptionNew | NSKeyValueObservingOptionOld;
[self.person1 addObserver:self forKeyPath:@"age" options:options context:@"123"];
}
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
// NSKVONotifying_MJPerson是使用Runtime动态创建的一个类，是MJPerson的子类
// self.person1.isa == NSKVONotifying_MJPerson
[self.person1 setAge:21];
// self.person2.isa = MJPerson
// [self.person2 setAge:22];
}
- (void)dealloc {
[self.person1 removeObserver:self forKeyPath:@"age"];
}
// 当监听对象的属性值发生改变时，就会调用
- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context
{
NSLog(@"监听到%@的%@属性值改变了 - %@ - %@", object, keyPath, change, context);
}
@end
- class、dealloc、_isKVOA的作用和实现
添加kvo监听后系统会自动生成隐藏NSKVONotifying_MJPerson类，里面的方法时看不到的。
- 打印类对象的所有方法名：
#import "ViewController.h"
#import "MJPerson.h"
#import
@interface ViewController ()
@property (strong, nonatomic) MJPerson *person1;
@property (strong, nonatomic) MJPerson *person2;
@end
//@implementation NSObject
//
//- (Class)class
//{
// return object_getClass(self);
//}
//
//@end
// 反编译工具 - Hopper
@implementation ViewController
//传入一个类对象,打印这个类对象的所有方法名
- (void)printMethodNamesOfClass:(Class)cls
{
unsigned int count;
// 获得方法数组
Method *methodList = class_copyMethodList(cls, &count);
// 存储方法名
NSMutableString *methodNames = [NSMutableString string];
// 遍历所有的方法
for (int i = 0; i < count; i++) {
// 获得方法
Method method = methodList[i];
// 获得方法名
NSString *methodName = NSStringFromSelector(method_getName(method));
// 拼接方法名
[methodNames appendString:methodName];
[methodNames appendString:@", "];
}
// 释放（c语言创建的对象要手动释放）
free(methodList);
// 打印方法名
NSLog(@"%@ %@", cls, methodNames);
}
- (void)viewDidLoad {
[super viewDidLoad];
self.person1 = [[MJPerson alloc] init];
self.person1.age = 1;
self.person2 = [[MJPerson alloc] init];
self.person2.age = 2;
// 给person1对象添加KVO监听
NSKeyValueObservingOptions options = NSKeyValueObservingOptionNew | NSKeyValueObservingOptionOld;
[self.person1 addObserver:self forKeyPath:@"age" options:options context:@"123"];
[self printMethodNamesOfClass:object_getClass(self.person1)];
[self printMethodNamesOfClass:object_getClass(self.person2)];
}
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
// [self.person1 setAge:21];
[self.person1 willChangeValueForKey:@"age"];
[self.person1 didChangeValueForKey:@"age"];
}
- (void)dealloc {
[self.person1 removeObserver:self forKeyPath:@"age"];
}
// observeValueForKeyPath:ofObject:change:context:
// 当监听对象的属性值发生改变时，就会调用
- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context
{
NSLog(@"监听到%@的%@属性值改变了 - %@ - %@", object, keyPath, change, context);
}
@end