OC第九天笔记2016年03月24日（周四）A.M

 1 <font size="3"><font size="3">#import <Foundation/Foundation.h>
 2 #import "Student.h"
 3 
 4 int main(int argc, const char * argv[]) {
 5     @autoreleasepool {
 6         
 7         Student* s = [[Student alloc] init];
 8         [s setValue:@"语文" forKeyPath:@"course.courseName"];
 9         
10         [s print];
11         
12         //键：必须与实例变量同名
13         [s setValue:@"lily" forKey:@"name"];
14         [s print];
15         [s setValue:[NSNumber numberWithInt:10] forKey:@"age"];
16         [s print];
17         
18         //对课程设置
19         Course* c = [[Course alloc] init];
20         [c setValue:@"math" forKey:@"courseName"];
21         
22         [s setValue:c forKey:@"course"];
23         NSLog(@"%lu",[c retainCount]);
24         
25         //对s的课程名称进行修改
26         [s setValue:@"English" forKeyPath:@"course.courseName"];
27         [s print];
28         [s valueForKeyPath:@"course.courseName"];
29         
30         
31         NSLog(@"%@",[s valueForKey:@"name"]);
32         NSLog(@"%@",[s valueForKey:@"age"]);
33         
34         [c release];
35         [s release];
36         
37         //脱字符：^
38         //块的返回值类型（^块的名字）（形参列表);
39         //块的实现基本格式。
40         //^(形参列表){//实现语句}
41         __block int a = 20;//被__block修饰的变量可以在块中被修改，否则只能读取值
42         a++;
43         
44         int(^myblock)(int);
45         myblock = ^(int n){
46             NSLog(@"块");
47             return n+1;
48         };
49         NSLog(@"%d",myblock(10));//使用块。
50         
51     }
52     return 0;
53 }
54 </font></font>

 1 <font size="3">#import <Foundation/Foundation.h>
 2 #import "Course.h"
 3 
 4 //kvc kvo:course.courseName 学生：观察者
 5 
 6 @interface Student : NSObject
 7 {
 8     NSString* name;
 9     int age;
10     Course* course;
11 }
12 
13 -(void)print;
14 
15 @end</font>

 1 <font size="3">#import "Student.h"
 2 
 3 @implementation Student
 4 
 5 -(id)init
 6 {
 7     if (self = [super init]) {
 8         name = [[NSString alloc] initWithFormat:@"lily"];
 9         course = [[Course alloc] init];
10         age = 0;
11     }
12     //添加观察者，  观察者：学生 观察的实例变量：course.courseName
13     [course addObserver:self forKeyPath:@"courseName" options:NSKeyValueObservingOptionOld|NSKeyValueObservingOptionNew context:NULL];
14     return self;
15 }
16 
17 
18 //一旦观察者观察的实例变量变化，此方法会被回调
19 
20 -(void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary<NSString *,id> *)change context:(void *)context
21 {
22 //    NSLog(@"%@",change);
23     NSLog(@"新的课程名称发生变化了，为：%@",[change objectForKey:@"new"]);
24     NSLog(@"旧的课程名称发生变化了，为：%@",[change objectForKey:@"old"]);
25 }
26 
27 -(void)print
28 {
29     NSLog(@"name: %@  age: %d", name, age);
30     [course print];//代码复用
31 }
32 
33 -(void)dealloc
34 {
35     //移除观察者
36     [course removeObserver:self forKeyPath:@"courseName"];
37     [name release];
38     [course release];
39     [super dealloc];
40 }
41 
42 @end</font>

1 <font size="3">#import <Foundation/Foundation.h>
2 
3 @interface Course : NSObject
4 {
5     NSString* courseName;
6 }
7 -(void)print;
8 @end</font>

 1 <font size="3">#import "Course.h"
 2 
 3 @implementation Course
 4 
 5 -(void)print
 6 {
 7     NSLog(@"coursename%@",courseName);
 8 }
 9 
10 -(void)dealloc
11 {
12     [courseName release];
13     [super dealloc];
14 }
15 
16 @end
17 </font>