NSDictionary 、 NSMutableDictionary

1 重构学生与学校的练习

1.1 问题

本案例要求用字典解决下述问题。问题是：有一个学校，该学校有两个学院，每个学院中又有两个班级，而在每个班级中有两名学生。

现在作如下要求：

1)显示所有学生的信息。

2)只显示姓名为“zhangsan”的学生的信息。

3)只显示年龄为18岁的学生的信息。

4)如果每个学生有本书，显示所有学生的书的名称和价格。

1.2 步骤

实现此案例需要按照如下步骤进行。

步骤一：定义类Book

首先，在Day04工程中新添加Book.h文件，用于定义新的类Book。

代码如下所示：

 

1. #import <Foundation/Foundation.h>
3. @interface Book : NSObject<NSCopying>
5. @property(nonatomic, copy)NSString *name;
6. @property(nonatomic,assign)int price;
8. @end

在上述代码中，以下代码：

 

1. @interface Book : NSObject<NSCopying>

定义了类Book，该类采用了NSCopying协议。

在上述代码中，以下代码：

1. @property(nonatomic, copy)NSString *name;

在Book类中定义的属性name是NSString类的对象，用于存储书的名字。它有两个参数，一个是nonatomic，它代表对属性赋值的时候不加锁，即在多线程环境下访问时可能会出现数据错误，如果需要在多线程环境下运行，为保证数据不会出现错误，可使用atomic参数，它会在对属性赋值的时候加锁。另一个参数是copy，该参数一般用于NSObject类及其子类的对象，这些对象在赋值时实现深拷贝，即属性name指向的对象是赋值给它的对象的副本。

在上述代码中，以下代码：

1. @property(nonatomic,assign)int price;

在Book类中定义的整型属性price，用于存储书的价格。它有两个参数，一个是nonatomic，另一个参数是assign，对于C语言的基本数据类型，只能选取这个参数。

然后，在类Book的实现部分，即在Book.m文件中，添加两个方法的实现，一个是copyWithZone方法，该方法是在NSCopying协议中声明的方法，用于深拷贝；另一个是dealloc方法，由于使用ARC，该方法在本类中实际上没有任何实际意义，只是在类的对象销毁时，在控制台上输出一个提示。

代码如下所示：

1. #import "Book.h"
3. @implementation Book
5. -(id)copyWithZone:(NSZone*)zone
6. {
7. Book* book = [[Book allocWithZone:zone] init];
8. book.name = self.name;
9. book.price = self.price;
10. return book;
11. }
13. -(void)dealloc{
14. NSLog(@"书对象销毁了 price:%d",self.price);
15. }
17. @end

上述代码中，copyWithZone方法不能在类外直接被调用，它是在向一个对象发送copy消息时，由copy消息调用。在该方法中，以下代码：

1. Book* book = [[Book allocWithZone:zone] init];
2. book.name = self.name;
3. book.price = self.price;

生成一个本类对象的副本。需要注意的是分配空间使用的是allocWithZone方法。

上述代码中，dealloc方法也不能在类外直接被调用，它是在一个对象被release并且对象的引用计数为0时，由内存管理程序调用的方法。

步骤二：定义类TRStudent

首先，在Day04工程中新添加TRStudent.h文件，用于定义新的类TRStudent。

代码如下所示：

1. #import <Foundation/Foundation.h>
2. #import "Book.h"
4. @interface TRStudent : NSObject
6. @property(nonatomic,assign)int age;
7. @property(nonatomic,copy)NSString* name;
8. @property(nonatomic,copy)Book *book;
10. -(id)initWithAge:(int)age andName:(NSString*)name andBook:(Book*)book;
11. +(id)studentWithAge:(int)age andName:(NSString*)name andBook:(Book*)book;
12. -(void)print:(id)condition;
14. @end

在上述代码中，定义了类Student，在类中有三个带参属性。

一个属性是整型变量age，如下代码所示：

1. @property(nonatomic,assign) int age;

用于存储学生的年龄。

另一个属性是name，如下代码所示：

1. @property(nonatomic,copy)NSString* name;

用于存储学生的姓名。

最后一个属性是book，如下代码所示：

1. @property(nonatomic,copy)Book *book;

用于存储学生正在学习的书。值得注意的是，Book类采纳NSCopying协议，是因为此处使用了copy这个属性参数。

上述代码中，以下代码：

1. -(id)initWithAge:(int)age andName:(NSString*)name andBook:(Book*)book;
2. +(id)studentWithAge:(int)age andName:(NSString*)name andBook:(Book*)book;

声明了TRStudent类的带参初始化方法和带参工厂方法。

上述代码中，以下代码：

1. -(void)print:(id)condition;

声明了一个print方法，该方法用于根据形参condition的不同，打印不同的TRStudent类对象的属性值。

然后，在类Student的实现部分，即在Student.m文件中，添加带参初始化方法和工厂初始化方法以及print方法的实现。

代码如下所示：

1. #import "TRStudent.h"
3. @implementation TRStudent
5. -(id)initWithAge:(int)age
6. andName:(NSString*)name
7. andBook:(Book*)book{
8. self = [super init];
9. if (self) {
10. self.age = age;
11. self.name = name;
12. self.book = book;
13. }
14. return self;
15. }
17. +(id)studentWithAge:(int)age
18. andName:(NSString*)name
19. andBook:(Book*)book{
20. return [[TRStudent alloc]initWithAge:age andName:name andBook:book];
21. }
23. -(void)print:(id)condition
24. {
25. bool a = [condition isKindOfClass:[NSNumber class]];
26. bool b = [condition intValue] == self.age;
27. bool c = [condition isKindOfClass:[NSString class]];
28. bool d = [self.name isEqualToString:condition];
29. if ((a && b) || (c && d))
30. NSLog(@"stu name:%@, age:%d", self.name, self.age);
31. }
33. @end

上述代码中，以下代码：

1. bool a = [condition isKindOfClass:[NSNumber class]];
2. bool b = [condition intValue] == self.age;

定义了两个bool类型的变量。

变量a被赋值为形参condition是否是NSNumber类对象的判断结果，其中方法isKindOfClass的作用是判断对象condition是否是NSNumber类的对象。方法isKindOfClass的形参为Class类型的值，该类型的值通过工厂方法class获得。

变量b被赋值为形参condition的值是否与当前对象age属性值相等的判断结果。通过向形参condition发送intValue消息，如果condition的值为数字字符串，则将其转换成整型数据。

上述代码中，以下代码：

1. bool c = [condition isKindOfClass:[NSString class]];
2. bool d = [self.name isEqualToString:condition];

定义了两个bool类型的变量。

变量c被赋值为形参condition是否是NSString类对象的判断结果。

变量d被赋值为当前对象name属性值是否与形参condition的值相等的判断结果。方法isEqualToString是NSString类的方法，用于判断两个字符串是否相等。

上述代码中，以下代码：

1. if ((a && b) || (c && d))
2. NSLog(@"stu name:%@, age:%d", self.name, self.age);

如果条件(a && b)为真则表示形参condition为NSNumber类的对象并且将其拆箱后的值与当前对象age属性值相等。

如果条件(c && d)为真则表示形参condition为NSString类的对象并且与当前对象name属性值是同一字符串。

步骤三：在主程序中创建八个学生对象

代码如下所示：

1. #import <Foundation/Foundation.h>
2. #import "TRStudent.h"
4. int main(int argc, const char * argv[])
5. {
7. @autoreleasepool {
9. // insert code here...
10. //创建学生对象
11. Book* book1 = [[Book alloc] init];
12. book1.name = @"sanguo";
13. book1.price = 20;
14. TRStudent* stu1 = [TRStudent studentWithAge:18 andName:@"zhangsan" andBook:book1];
16. Book* book2 = [[Book alloc] init];
17. book2.name = @"shuihu";
18. book2.price = 18;
19. TRStudent* stu2 = [TRStudent studentWithAge:19 andName:@"lisi" andBook:book2];
21. Book* book3 = [[Book alloc] init];
22. book3.name = @"xiyouji";
23. book3.price = 28;
24. TRStudent* stu3 = [TRStudent studentWithAge:20 andName:@"wangwu" andBook:book3];
26. Book* book4 = [[Book alloc] init];
27. book4.name = @"hongluomeng";
28. book4.price = 24;
29. TRStudent* stu4 = [TRStudent studentWithAge:21 andName:@"zhaoliu" andBook:book4];
31. Book* book5 = [[Book alloc] init];
32. book5.name = @"fengshenyanyi";
33. book5.price = 22;
34. TRStudent* stu5 = [TRStudent studentWithAge:22 andName:@"qianqi" andBook:book5];
36. Book* book6 = [[Book alloc] init];
37. book6.name = @"liaozhaizhiyi";
38. book6.price = 15;
39. TRStudent* stu6 = [TRStudent studentWithAge:23 andName:@"zhangfei" andBook:book6];
41. Book* book7 = [[Book alloc] init];
42. book7.name = @"sanxiawuyi";
43. book7.price = 17;
44. TRStudent* stu7 = [TRStudent studentWithAge:24 andName:@"guanyu" andBook:book7];
46. Book* book8 = [[Book alloc] init];
47. book8.name = @"yuefeizhuan";
48. book8.price = 27;
49. TRStudent* stu8 = [TRStudent studentWithAge:25 andName:@"zhaoyun" andBook:book8];
51. }
52. return 0;
53. }

上述代码中，以下代码：

1. //创建学生对象
2. Book* book1 = [[Book alloc] init];
3. book1.name = @"sanguo";
4. book1.price = 20;
5. TRStudent* stu1 = [TRStudent studentWithAge:18 andName:@"zhangsan" andBook:book1];

首先创建了一个Book类的对象book1，然后使用工厂方法studentWithAge：andName：andBook：创建TRStudent类的对象stu1。

步骤四：在主程序中创建班级字典

代码如下所示：

1. #import <Foundation/Foundation.h>
2. #import "TRStudent.h"
4. int main(int argc, const char * argv[])
5. {
7. @autoreleasepool {
9. // insert code here...
10. //创建学生对象
11. Book* book1 = [[Book alloc] init];
12. book1.name = @"sanguo";
13. book1.price = 20;
14. TRStudent* stu1 = [TRStudent studentWithAge:18 andName:@"zhangsan" andBook:book1];
16. Book* book2 = [[Book alloc] init];
17. book2.name = @"shuihu";
18. book2.price = 18;
19. TRStudent* stu2 = [TRStudent studentWithAge:19 andName:@"lisi" andBook:book2];
21. Book* book3 = [[Book alloc] init];
22. book3.name = @"xiyouji";
23. book3.price = 28;
24. TRStudent* stu3 = [TRStudent studentWithAge:20 andName:@"wangwu" andBook:book3];
26. Book* book4 = [[Book alloc] init];
27. book4.name = @"hongluomeng";
28. book4.price = 24;
29. TRStudent* stu4 = [TRStudent studentWithAge:21 andName:@"zhaoliu" andBook:book4];
31. Book* book5 = [[Book alloc] init];
32. book5.name = @"fengshenyanyi";
33. book5.price = 22;
34. TRStudent* stu5 = [TRStudent studentWithAge:22 andName:@"qianqi" andBook:book5];
36. Book* book6 = [[Book alloc] init];
37. book6.name = @"liaozhaizhiyi";
38. book6.price = 15;
39. TRStudent* stu6 = [TRStudent studentWithAge:23 andName:@"zhangfei" andBook:book6];
41. Book* book7 = [[Book alloc] init];
42. book7.name = @"sanxiawuyi";
43. book7.price = 17;
44. TRStudent* stu7 = [TRStudent studentWithAge:24 andName:@"guanyu" andBook:book7];
46. Book* book8 = [[Book alloc] init];
47. book8.name = @"yuefeizhuan";
48. book8.price = 27;
49. TRStudent* stu8 = [TRStudent studentWithAge:25 andName:@"zhaoyun" andBook:book8];
51. //班级
52. NSDictionary* class1403A = [NSDictionary dictionaryWithObjectsAndKeys:stu1, @"1", stu2, @"2", nil];
53. NSDictionary* class1403B = [NSDictionary dictionaryWithObjectsAndKeys:stu3, @"1", stu4, @"2", nil];
54. NSDictionary* class1403C = [NSDictionary dictionaryWithObjectsAndKeys:stu5, @"1", stu6, @"2", nil];
55. NSDictionary* class1403D = [NSDictionary dictionaryWithObjectsAndKeys:stu7, @"1", stu8, @"2", nil];
57. }
58. return 0;
59. }

上述代码中，以下代码：

1. //班级
2. NSDictionary* class1403A = [NSDictionary dictionaryWithObjectsAndKeys:stu1, @"1", stu2, @"2", nil];
3. NSDictionary* class1403B = [NSDictionary dictionaryWithObjectsAndKeys:stu3, @"1", stu4, @"2", nil];
4. NSDictionary* class1403C = [NSDictionary dictionaryWithObjectsAndKeys:stu5, @"1", stu6, @"2", nil];
5. NSDictionary* class1403D = [NSDictionary dictionaryWithObjectsAndKeys:stu7, @"1", stu8, @"2", nil];

创建了四个字典对象，每个字典对象为一个班级，班级中有两个学生作为字典的值value，并为其定义了编号@“1”和@“2”作为关键字key。其中使用工厂方法dictionaryWithObjectsAndKeys：创建字典对象。值得注意的是，在形参的最后是nil，它代表放入字典中的键值对结束。

步骤五：在主程序中创建学院和学校

代码如下所示：

1. #import <Foundation/Foundation.h>
2. #import "TRStudent.h"
4. int main(int argc, const char * argv[])
5. {
7. @autoreleasepool {
9. // insert code here...
10. //创建学生对象
11. Book* book1 = [[Book alloc] init];
12. book1.name = @"sanguo";
13. book1.price = 20;
14. TRStudent* stu1 = [TRStudent studentWithAge:18 andName:@"zhangsan" andBook:book1];
16. Book* book2 = [[Book alloc] init];
17. book2.name = @"shuihu";
18. book2.price = 18;
19. TRStudent* stu2 = [TRStudent studentWithAge:19 andName:@"lisi" andBook:book2];
21. Book* book3 = [[Book alloc] init];
22. book3.name = @"xiyouji";
23. book3.price = 28;
24. TRStudent* stu3 = [TRStudent studentWithAge:20 andName:@"wangwu" andBook:book3];
26. Book* book4 = [[Book alloc] init];
27. book4.name = @"hongluomeng";
28. book4.price = 24;
29. TRStudent* stu4 = [TRStudent studentWithAge:21 andName:@"zhaoliu" andBook:book4];
31. Book* book5 = [[Book alloc] init];
32. book5.name = @"fengshenyanyi";
33. book5.price = 22;
34. TRStudent* stu5 = [TRStudent studentWithAge:22 andName:@"qianqi" andBook:book5];
36. Book* book6 = [[Book alloc] init];
37. book6.name = @"liaozhaizhiyi";
38. book6.price = 15;
39. TRStudent* stu6 = [TRStudent studentWithAge:23 andName:@"zhangfei" andBook:book6];
41. Book* book7 = [[Book alloc] init];
42. book7.name = @"sanxiawuyi";
43. book7.price = 17;
44. TRStudent* stu7 = [TRStudent studentWithAge:24 andName:@"guanyu" andBook:book7];
46. Book* book8 = [[Book alloc] init];
47. book8.name = @"yuefeizhuan";
48. book8.price = 27;
49. TRStudent* stu8 = [TRStudent studentWithAge:25 andName:@"zhaoyun" andBook:book8];
51. //班级
52. NSDictionary* class1403A = [NSDictionary dictionaryWithObjectsAndKeys:stu1, @"1", stu2, @"2", nil];
53. NSDictionary* class1403B = [NSDictionary dictionaryWithObjectsAndKeys:stu3, @"1", stu4, @"2", nil];
54. NSDictionary* class1403C = [NSDictionary dictionaryWithObjectsAndKeys:stu5, @"1", stu6, @"2", nil];
55. NSDictionary* class1403D = [NSDictionary dictionaryWithObjectsAndKeys:stu7, @"1", stu8, @"2", nil];
57. //学院
58. NSDictionary* college3G = [NSDictionary dictionaryWithObjectsAndKeys:class1403A, @"1", class1403B, @"2", nil];
59. NSDictionary* collegeTest = [NSDictionary dictionaryWithObjectsAndKeys:class1403C, @"1", class1403D, @"2", nil];
61. //学校
62. NSDictionary* tarena = [NSDictionary dictionaryWithObjectsAndKeys:college3G, @"1", collegeTest, @"2", nil];
64. }
65. return 0;
66. }

上述代码中，以下代码：

1. //学院
2. NSDictionary* college3G = [NSDictionary dictionaryWithObjectsAndKeys:class1403A, @"1", class1403B, @"2", nil];
3. NSDictionary* collegeTest = [NSDictionary dictionaryWithObjectsAndKeys:class1403C, @"1", class1403D, @"2", nil];
5. //学校
6. NSDictionary* tarena = [NSDictionary dictionaryWithObjectsAndKeys:college3G, @"1", collegeTest, @"2", nil];

创建了两个学院字典，每个学院字典中有两个班级字典作为字典的值value，并为其定义了编号@“1”和@“2”作为关键字key。还创建了一个学校字典，其中包含上述两个学院字典作为字典的值value，并为其定义了编号@“1”和@“2”作为关键字key。

步骤六：在主程序中遍历输出所有学生信息

代码如下所示：

1. #import <Foundation/Foundation.h>
2. #import "TRStudent.h"
4. int main(int argc, const char * argv[])
5. {
7. @autoreleasepool {
9. // insert code here...
10. //创建学生对象
11. Book* book1 = [[Book alloc] init];
12. book1.name = @"sanguo";
13. book1.price = 20;
14. TRStudent* stu1 = [TRStudent studentWithAge:18 andName:@"zhangsan" andBook:book1];
16. Book* book2 = [[Book alloc] init];
17. book2.name = @"shuihu";
18. book2.price = 18;
19. TRStudent* stu2 = [TRStudent studentWithAge:19 andName:@"lisi" andBook:book2];
21. Book* book3 = [[Book alloc] init];
22. book3.name = @"xiyouji";
23. book3.price = 28;
24. TRStudent* stu3 = [TRStudent studentWithAge:20 andName:@"wangwu" andBook:book3];
26. Book* book4 = [[Book alloc] init];
27. book4.name = @"hongluomeng";
28. book4.price = 24;
29. TRStudent* stu4 = [TRStudent studentWithAge:21 andName:@"zhaoliu" andBook:book4];
31. Book* book5 = [[Book alloc] init];
32. book5.name = @"fengshenyanyi";
33. book5.price = 22;
34. TRStudent* stu5 = [TRStudent studentWithAge:22 andName:@"qianqi" andBook:book5];
36. Book* book6 = [[Book alloc] init];
37. book6.name = @"liaozhaizhiyi";
38. book6.price = 15;
39. TRStudent* stu6 = [TRStudent studentWithAge:23 andName:@"zhangfei" andBook:book6];
41. Book* book7 = [[Book alloc] init];
42. book7.name = @"sanxiawuyi";
43. book7.price = 17;
44. TRStudent* stu7 = [TRStudent studentWithAge:24 andName:@"guanyu" andBook:book7];
46. Book* book8 = [[Book alloc] init];
47. book8.name = @"yuefeizhuan";
48. book8.price = 27;
49. TRStudent* stu8 = [TRStudent studentWithAge:25 andName:@"zhaoyun" andBook:book8];
51. //班级
52. NSDictionary* class1403A = [NSDictionary dictionaryWithObjectsAndKeys:stu1, @"1", stu2, @"2", nil];
53. NSDictionary* class1403B = [NSDictionary dictionaryWithObjectsAndKeys:stu3, @"1", stu4, @"2", nil];
54. NSDictionary* class1403C = [NSDictionary dictionaryWithObjectsAndKeys:stu5, @"1", stu6, @"2", nil];
55. NSDictionary* class1403D = [NSDictionary dictionaryWithObjectsAndKeys:stu7, @"1", stu8, @"2", nil];
57. //学院
58. NSDictionary* college3G = [NSDictionary dictionaryWithObjectsAndKeys:class1403A, @"1", class1403B, @"2", nil];
59. NSDictionary* collegeTest = [NSDictionary dictionaryWithObjectsAndKeys:class1403C, @"1", class1403D, @"2", nil];
61. //学校
62. NSDictionary* tarena = [NSDictionary dictionaryWithObjectsAndKeys:college3G, @"1", collegeTest, @"2", nil];
64. //遍历学校
65. NSEnumerator *e = [tarena objectEnumerator];
66. NSDictionary* college;
67. while (college = [e nextObject])
68. {
69. //遍历学院
70. NSEnumerator *e1 = [college objectEnumerator];
71. NSDictionary* class;
72. while (class = [e1 nextObject])
73. {
74. //遍历班级
75. NSEnumerator *e2 = [class objectEnumerator];
76. TRStudent* stu;
77. while (stu = [e2 nextObject])
78. {
79. NSLog(@"stu name:%@, age:%d", stu.name, stu.age);
80. }
81. }
82. }
84. }
85. return 0;
86. }

上述代码中，以下代码：

1. //遍历学校
2. NSEnumerator *e = [tarena objectEnumerator];
3. NSDictionary* college;
4. while (college = [e nextObject])
5. {
6. //遍历学院
7. NSEnumerator *e1 = [college objectEnumerator];
8. NSDictionary* class;
9. while (class = [e1 nextObject])
10. {
11. //遍历班级
12. NSEnumerator *e2 = [class objectEnumerator];
13. TRStudent* stu;
14. while (stu = [e2 nextObject])
15. {
16. NSLog(@"stu name:%@, age:%d", stu.name, stu.age);
17. }
18. }
19. }

通过三重枚举遍历方法遍历所有学生的信息。以下代码：

1. //遍历学校
2. NSEnumerator *e = [tarena objectEnumerator];

是通过NSDictionary类的objectEnumerator方法，获取学校tarena的值value的枚举器。

以下代码：

1. NSDictionary* college;
2. while (college = [e nextObject])

是通过NSEnumerator类的nextObject方法，使用循环逐个获取学校tarena中的每一个值value对象。

以下代码：

1. //遍历学院
2. NSEnumerator *e1 = [college objectEnumerator];
3. NSDictionary* class;
4. while (class = [e1 nextObject])

是通过建立学院college的值value枚举器，使用循环逐个获得每一个值value对象。

以下代码：

1. //遍历班级
2. NSEnumerator *e2 = [class objectEnumerator];
3. TRStudent* stu;
4. while (stu = [e2 nextObject])

是通过建立班级class的值value枚举器，使用循环逐个获得每一个值value对象。

步骤七：在主程序中遍历显示指定条件的学生信息

代码如下所示：

1. #import <Foundation/Foundation.h>
2. #import "TRStudent.h"
4. int main(int argc, const char * argv[])
5. {
7. @autoreleasepool {
9. // insert code here...
10. //创建学生对象
11. Book* book1 = [[Book alloc] init];
12. book1.name = @"sanguo";
13. book1.price = 20;
14. TRStudent* stu1 = [TRStudent studentWithAge:18 andName:@"zhangsan" andBook:book1];
16. Book* book2 = [[Book alloc] init];
17. book2.name = @"shuihu";
18. book2.price = 18;
19. TRStudent* stu2 = [TRStudent studentWithAge:19 andName:@"lisi" andBook:book2];
21. Book* book3 = [[Book alloc] init];
22. book3.name = @"xiyouji";
23. book3.price = 28;
24. TRStudent* stu3 = [TRStudent studentWithAge:20 andName:@"wangwu" andBook:book3];
26. Book* book4 = [[Book alloc] init];
27. book4.name = @"hongluomeng";
28. book4.price = 24;
29. TRStudent* stu4 = [TRStudent studentWithAge:21 andName:@"zhaoliu" andBook:book4];
31. Book* book5 = [[Book alloc] init];
32. book5.name = @"fengshenyanyi";
33. book5.price = 22;
34. TRStudent* stu5 = [TRStudent studentWithAge:22 andName:@"qianqi" andBook:book5];
36. Book* book6 = [[Book alloc] init];
37. book6.name = @"liaozhaizhiyi";
38. book6.price = 15;
39. TRStudent* stu6 = [TRStudent studentWithAge:23 andName:@"zhangfei" andBook:book6];
41. Book* book7 = [[Book alloc] init];
42. book7.name = @"sanxiawuyi";
43. book7.price = 17;
44. TRStudent* stu7 = [TRStudent studentWithAge:24 andName:@"guanyu" andBook:book7];
46. Book* book8 = [[Book alloc] init];
47. book8.name = @"yuefeizhuan";
48. book8.price = 27;
49. TRStudent* stu8 = [TRStudent studentWithAge:25 andName:@"zhaoyun" andBook:book8];
51. //班级
52. NSDictionary* class1403A = [NSDictionary dictionaryWithObjectsAndKeys:stu1, @"1", stu2, @"2", nil];
53. NSDictionary* class1403B = [NSDictionary dictionaryWithObjectsAndKeys:stu3, @"1", stu4, @"2", nil];
54. NSDictionary* class1403C = [NSDictionary dictionaryWithObjectsAndKeys:stu5, @"1", stu6, @"2", nil];
55. NSDictionary* class1403D = [NSDictionary dictionaryWithObjectsAndKeys:stu7, @"1", stu8, @"2", nil];
57. //学院
58. NSDictionary* college3G = [NSDictionary dictionaryWithObjectsAndKeys:class1403A, @"1", class1403B, @"2", nil];
59. NSDictionary* collegeTest = [NSDictionary dictionaryWithObjectsAndKeys:class1403C, @"1", class1403D, @"2", nil];
61. //学校
62. NSDictionary* tarena = [NSDictionary dictionaryWithObjectsAndKeys:college3G, @"1", collegeTest, @"2", nil];
64. //遍历学校
65. NSEnumerator *e = [tarena objectEnumerator];
66. NSDictionary* college;
67. while (college = [e nextObject])
68. {
69. //遍历学院
70. NSEnumerator *e1 = [college objectEnumerator];
71. NSDictionary* class;
72. while (class = [e1 nextObject])
73. {
74. //遍历班级
75. NSEnumerator *e2 = [class objectEnumerator];
76. TRStudent* stu;
77. while (stu = [e2 nextObject])
78. {
79. NSLog(@"stu name:%@, age:%d", stu.name, stu.age);
80. }
81. }
82. }
84. //遍历学校
85. e = [tarena objectEnumerator];
86. while (college = [e nextObject])
87. {
88. //遍历学院
89. NSEnumerator *e1 = [college objectEnumerator];
90. NSDictionary* class;
91. while (class = [e1 nextObject])
92. {
93. //遍历班级
94. NSEnumerator *e2 = [class objectEnumerator];
95. TRStudent* stu;
96. while (stu = [e2 nextObject])
97. {
98. //输出年龄为18岁的学生信息
99. [stu print:[NSNumber numberWithInt:18]];
100. //输出姓名为“张三”的学生信息
101. [stu print:@"zhangsan"];
102. }
103. }
104. }
105. }
106. return 0;
107. }

上述代码中，以下代码：

1. //输出年龄为18岁的学生信息
2. [stu print:[NSNumber numberWithInt:18]];
3. //输出姓名为“张三”的学生信息
4. [stu print:@"zhangsan"];

调用TRSTudent的print：方法，有选择的打印对象stu的信息。print：方法有一个实参[NSNumber numberWithInt:18]作为选择的条件，如若条件成立，则打印对象stu的属性。

步骤八：在主程序中显示所有学生的书的名称和价格

代码如下所示：

1. #import <Foundation/Foundation.h>
2. #import "TRStudent.h"
4. int main(int argc, const char * argv[])
5. {
7. @autoreleasepool {
9. // insert code here...
10. //创建学生对象
11. Book* book1 = [[Book alloc] init];
12. book1.name = @"sanguo";
13. book1.price = 20;
14. TRStudent* stu1 = [TRStudent studentWithAge:18 andName:@"zhangsan" andBook:book1];
16. Book* book2 = [[Book alloc] init];
17. book2.name = @"shuihu";
18. book2.price = 18;
19. TRStudent* stu2 = [TRStudent studentWithAge:19 andName:@"lisi" andBook:book2];
21. Book* book3 = [[Book alloc] init];
22. book3.name = @"xiyouji";
23. book3.price = 28;
24. TRStudent* stu3 = [TRStudent studentWithAge:20 andName:@"wangwu" andBook:book3];
26. Book* book4 = [[Book alloc] init];
27. book4.name = @"hongluomeng";
28. book4.price = 24;
29. TRStudent* stu4 = [TRStudent studentWithAge:21 andName:@"zhaoliu" andBook:book4];
31. Book* book5 = [[Book alloc] init];
32. book5.name = @"fengshenyanyi";
33. book5.price = 22;
34. TRStudent* stu5 = [TRStudent studentWithAge:22 andName:@"qianqi" andBook:book5];
36. Book* book6 = [[Book alloc] init];
37. book6.name = @"liaozhaizhiyi";
38. book6.price = 15;
39. TRStudent* stu6 = [TRStudent studentWithAge:23 andName:@"zhangfei" andBook:book6];
41. Book* book7 = [[Book alloc] init];
42. book7.name = @"sanxiawuyi";
43. book7.price = 17;
44. TRStudent* stu7 = [TRStudent studentWithAge:24 andName:@"guanyu" andBook:book7];
46. Book* book8 = [[Book alloc] init];
47. book8.name = @"yuefeizhuan";
48. book8.price = 27;
49. TRStudent* stu8 = [TRStudent studentWithAge:25 andName:@"zhaoyun" andBook:book8];
51. //班级
52. NSDictionary* class1403A = [NSDictionary dictionaryWithObjectsAndKeys:stu1, @"1", stu2, @"2", nil];
53. NSDictionary* class1403B = [NSDictionary dictionaryWithObjectsAndKeys:stu3, @"1", stu4, @"2", nil];
54. NSDictionary* class1403C = [NSDictionary dictionaryWithObjectsAndKeys:stu5, @"1", stu6, @"2", nil];
55. NSDictionary* class1403D = [NSDictionary dictionaryWithObjectsAndKeys:stu7, @"1", stu8, @"2", nil];
57. //学院
58. NSDictionary* college3G = [NSDictionary dictionaryWithObjectsAndKeys:class1403A, @"1", class1403B, @"2", nil];
59. NSDictionary* collegeTest = [NSDictionary dictionaryWithObjectsAndKeys:class1403C, @"1", class1403D, @"2", nil];
61. //学校
62. NSDictionary* tarena = [NSDictionary dictionaryWithObjectsAndKeys:college3G, @"1", collegeTest, @"2", nil];
64. //遍历学校
65. NSEnumerator *e = [tarena objectEnumerator];
66. NSDictionary* college;
67. while (college = [e nextObject])
68. {
69. //遍历学院
70. NSEnumerator *e1 = [college objectEnumerator];
71. NSDictionary* class;
72. while (class = [e1 nextObject])
73. {
74. //遍历班级
75. NSEnumerator *e2 = [class objectEnumerator];
76. TRStudent* stu;
77. while (stu = [e2 nextObject])
78. {
79. NSLog(@"stu name:%@, age:%d", stu.name, stu.age);
80. }
81. }
82. }
84. //遍历学校
85. e = [tarena objectEnumerator];
86. while (college = [e nextObject])
87. {
88. //遍历学院
89. NSEnumerator *e1 = [college objectEnumerator];
90. NSDictionary* class;
91. while (class = [e1 nextObject])
92. {
93. //遍历班级
94. NSEnumerator *e2 = [class objectEnumerator];
95. TRStudent* stu;
96. while (stu = [e2 nextObject])
97. {
98. //输出年龄为18岁的学生信息
99. [stu print:[NSNumber numberWithInt:18]];
100. //输出姓名为“张三”的学生信息
101. [stu print:@"zhangsan"];
102. }
103. }
104. }
106. //遍历学校
107. e = [tarena objectEnumerator];
108. while (college = [e nextObject])
109. {
110. //遍历学院
111. NSEnumerator *e1 = [college objectEnumerator];
112. NSDictionary* class;
113. while (class = [e1 nextObject])
114. {
115. //遍历班级
116. NSEnumerator *e2 = [class objectEnumerator];
117. TRStudent* stu;
118. while (stu = [e2 nextObject])
119. {
120. NSLog(@"book name:%@, price:%d", stu.book.name, stu.book.price);
121. }
122. }
123. }
124. }
125. return 0;
126. }

上述代码再一次使用了三重枚举遍历，这一次与步骤六（遍历输出所有学生信息）中的三重枚举遍历相比，区别是最后使用NSLog输出为书的名称和价格，不是学生的姓名和年龄。

1.3 完整代码

本案例中，类Book声明，即Book.h文件，完整代码如下所示：

1. #import <Foundation/Foundation.h>
3. @interface Book : NSObject<NSCopying>
5. @property(nonatomic, copy)NSString *name;
6. @property(nonatomic,assign)int price;
8. @end

类Book实现，即Book.m文件，完整代码如下所示：

1. #import "Book.h"
3. @implementation Book
5. -(id)copyWithZone:(NSZone*)zone
6. {
7. Book* book = [[Book allocWithZone:zone] init];
8. book.name = self.name;
9. book.price = self.price;
10. return book;
11. }
13. -(void)dealloc{
14. NSLog(@"书对象销毁了 price:%d",self.price);
15. }
17. @end

本案例中，类TRStudent声明，即TRStudent.h文件，完整代码如下所示：

1. #import <Foundation/Foundation.h>
2. #import "Book.h"
4. @interface TRStudent : NSObject
6. @property(nonatomic,assign)int age;
7. @property(nonatomic,copy)NSString* name;
8. @property(nonatomic,copy)Book *book;
10. -(id)initWithAge:(int)age andName:(NSString*)name andBook:(Book*)book;
11. +(id)studentWithAge:(int)age andName:(NSString*)name andBook:(Book*)book;
12. -(void)print:(id)condition;
14. @end

类TRStudent实现，即TRStudent.m文件，完整代码如下所示：

1. #import "TRStudent.h"
3. @implementation TRStudent
5. -(id)initWithAge:(int)age
6. andName:(NSString*)name
7. andBook:(Book*)book{
8. self = [super init];
9. if (self) {
10. self.age = age;
11. self.name = name;
12. self.book = book;
13. }
14. return self;
15. }
17. +(id)studentWithAge:(int)age
18. andName:(NSString*)name
19. andBook:(Book*)book{
20. return [[TRStudent alloc]initWithAge:age andName:name andBook:book];
21. }
23. -(void)print:(id)condition
24. {
25. bool a = [condition isKindOfClass:[NSNumber class]];
26. bool b = [condition intValue] == self.age;
27. bool c = [condition isKindOfClass:[NSString class]];
28. bool d = [self.name isEqualToString:condition];
29. if ((a && b) || (c && d))
30. NSLog(@"stu name:%@, age:%d", self.name, self.age);
31. }
33. @end

主程序，即main.m，完整代码如下所示：

1. #import <Foundation/Foundation.h>
2. #import "TRStudent.h"
4. int main(int argc, const char * argv[])
5. {
7. @autoreleasepool {
9. // insert code here...
10. //创建学生对象
11. Book* book1 = [[Book alloc] init];
12. book1.name = @"sanguo";
13. book1.price = 20;
14. TRStudent* stu1 = [TRStudent studentWithAge:18 andName:@"zhangsan" andBook:book1];
16. Book* book2 = [[Book alloc] init];
17. book2.name = @"shuihu";
18. book2.price = 18;
19. TRStudent* stu2 = [TRStudent studentWithAge:19 andName:@"lisi" andBook:book2];
21. Book* book3 = [[Book alloc] init];
22. book3.name = @"xiyouji";
23. book3.price = 28;
24. TRStudent* stu3 = [TRStudent studentWithAge:20 andName:@"wangwu" andBook:book3];
26. Book* book4 = [[Book alloc] init];
27. book4.name = @"hongluomeng";
28. book4.price = 24;
29. TRStudent* stu4 = [TRStudent studentWithAge:21 andName:@"zhaoliu" andBook:book4];
31. Book* book5 = [[Book alloc] init];
32. book5.name = @"fengshenyanyi";
33. book5.price = 22;
34. TRStudent* stu5 = [TRStudent studentWithAge:22 andName:@"qianqi" andBook:book5];
36. Book* book6 = [[Book alloc] init];
37. book6.name = @"liaozhaizhiyi";
38. book6.price = 15;
39. TRStudent* stu6 = [TRStudent studentWithAge:23 andName:@"zhangfei" andBook:book6];
41. Book* book7 = [[Book alloc] init];
42. book7.name = @"sanxiawuyi";
43. book7.price = 17;
44. TRStudent* stu7 = [TRStudent studentWithAge:24 andName:@"guanyu" andBook:book7];
46. Book* book8 = [[Book alloc] init];
47. book8.name = @"yuefeizhuan";
48. book8.price = 27;
49. TRStudent* stu8 = [TRStudent studentWithAge:25 andName:@"zhaoyun" andBook:book8];
51. //班级
52. NSDictionary* class1403A = [NSDictionary dictionaryWithObjectsAndKeys:stu1, @"1", stu2, @"2", nil];
53. NSDictionary* class1403B = [NSDictionary dictionaryWithObjectsAndKeys:stu3, @"1", stu4, @"2", nil];
54. NSDictionary* class1403C = [NSDictionary dictionaryWithObjectsAndKeys:stu5, @"1", stu6, @"2", nil];
55. NSDictionary* class1403D = [NSDictionary dictionaryWithObjectsAndKeys:stu7, @"1", stu8, @"2", nil];
57. //学院
58. NSDictionary* college3G = [NSDictionary dictionaryWithObjectsAndKeys:class1403A, @"1", class1403B, @"2", nil];
59. NSDictionary* collegeTest = [NSDictionary dictionaryWithObjectsAndKeys:class1403C, @"1", class1403D, @"2", nil];
61. //学校
62. NSDictionary* tarena = [NSDictionary dictionaryWithObjectsAndKeys:college3G, @"1", collegeTest, @"2", nil];
64. //遍历学校
65. NSEnumerator *e = [tarena objectEnumerator];
66. NSDictionary* college;
67. while (college = [e nextObject])
68. {
69. //遍历学院
70. NSEnumerator *e1 = [college objectEnumerator];
71. NSDictionary* class;
72. while (class = [e1 nextObject])
73. {
74. //遍历班级
75. NSEnumerator *e2 = [class objectEnumerator];
76. TRStudent* stu;
77. while (stu = [e2 nextObject])
78. {
79. NSLog(@"stu name:%@, age:%d", stu.name, stu.age);
80. }
81. }
82. }
84. //遍历学校
85. e = [tarena objectEnumerator];
86. while (college = [e nextObject])
87. {
88. //遍历学院
89. NSEnumerator *e1 = [college objectEnumerator];
90. NSDictionary* class;
91. while (class = [e1 nextObject])
92. {
93. //遍历班级
94. NSEnumerator *e2 = [class objectEnumerator];
95. TRStudent* stu;
96. while (stu = [e2 nextObject])
97. {
98. //输出年龄为18岁的学生信息
99. [stu print:[NSNumber numberWithInt:18]];
100. //输出姓名为“张三”的学生信息
101. [stu print:@"zhangsan"];
102. }
103. }
104. }
106. //遍历学校
107. e = [tarena objectEnumerator];
108. while (college = [e nextObject])
109. {
110. //遍历学院
111. NSEnumerator *e1 = [college objectEnumerator];
112. NSDictionary* class;
113. while (class = [e1 nextObject])
114. {
115. //遍历班级
116. NSEnumerator *e2 = [class objectEnumerator];
117. TRStudent* stu;
118. while (stu = [e2 nextObject])
119. {
120. NSLog(@"book name:%@, price:%d", stu.book.name, stu.book.price);
121. }
122. }
123. }
124. }
125. return 0;
126. }