1 创建五个学生对象，放入数组并遍历
1.1 问题
创建一个自定义类TRStudent，为该类生成五个对象。把这五个对象存入一个数组当中，然后遍历数组。
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TRStudent
首先，在Day03工程中新添加TRStudent.h文件，用于定义新的类TRStudent。
代码如下所示：
- #import <Foundation/Foundation.h>
- @interface TRStudent : NSObject
- @property(nonatomic,assign)int age;
- @property(nonatomic,copy)NSString* name;
- @end
在上述代码中，以下代码：
- @property(nonatomic,assign)int age;
- @property(nonatomic,copy)NSString* name;
在TRStudent类中定义了两个属性，一个是整型变量age，用于存储学生的年龄；另一个是NSString类的对象name，用于存储学生的姓名。
然后，在类TRStudent的实现部分，即在TRStudent.m文件中，重写description方法的实现，该方法用于在NSLog中用%@输出TRStudent类的对象值。
代码如下所示：
- #import "TRStudent.h"
- @implementation TRStudent
- -(NSString *)description{
- return [NSString stringWithFormat:@"age:%d",self.age];
- }
- @end
上述代码中，以下代码：
- -(NSString *)description{
- return [NSString stringWithFormat:@"student age:%d name:%@",self.age,self.name];
- }
是重写description方法的实现，该方法用于在NSLog中用%@输出TRStudent类的对象值。
步骤二：在主程序中定义五个学生对象
代码如下所示：
- #import <Foundation/Foundation.h>
- #import "TRStudent.h"
- int main(int argc, const char * argv[])
- {
- @autoreleasepool {
- // insert code here...
- TRStudent* stu = [[TRStudent alloc]init];
- stu.age = 18;
- stu.name = @"zhangsan";
- TRStudent* stu2 = [[TRStudent alloc]init];
- stu2.age = 20;
- stu2.name = @"lisi";
- TRStudent* stu3 = [[TRStudent alloc]init];
- stu3.age = 30;
- stu3.name = @"wangwu";
- TRStudent* stu4 = [[TRStudent alloc]init];
- stu4.age = 40;
- stu4.name = @"zhaoliu";
- TRStudent* stu5 = [[TRStudent alloc]init];
- stu5.age = 35;
- stu5.name = @"qianqi";
- }
- return 0;
- }
步骤三：使用五个学生对象生成一个可变数组
代码如下所示：
- #import <Foundation/Foundation.h>
- #import "TRStudent.h"
- int main(int argc, const char * argv[])
- {
- @autoreleasepool {
- // insert code here...
- TRStudent* stu = [[TRStudent alloc]init];
- stu.age = 18;
- stu.name = @"zhangsan";
- TRStudent* stu2 = [[TRStudent alloc]init];
- stu2.age = 20;
- stu2.name = @"lisi";
- TRStudent* stu3 = [[TRStudent alloc]init];
- stu3.age = 30;
- stu3.name = @"wangwu";
- TRStudent* stu4 = [[TRStudent alloc]init];
- stu4.age = 40;
- stu4.name = @"zhaoliu";
- TRStudent* stu5 = [[TRStudent alloc]init];
- stu5.age = 35;
- stu5.name = @"qianqi";
- NSMutableArray* students = [NSMutableArray arrayWithObjects:stu,stu2,stu3,stu4,stu5, nil];
- }
- return 0;
- }
上述代码中，以下代码：
- NSMutableArray* students = [NSMutableArray arrayWithObjects:stu,stu2,stu3,stu4,stu5, nil];
生成一个可变数组类NSMutableArray的对象students。并使用NSMutableArray类的方法arrayWithObjects将students初始化为上述五个学生对象。值得注意的是实参的最后是nil，它的作用是标志后面没有要初始化的对象了。
步骤四：对五个学生对象进行遍历
代码如下所示：
- #import <Foundation/Foundation.h>
- #import "TRStudent.h"
- int main(int argc, const char * argv[])
- {
- @autoreleasepool {
- // insert code here...
- TRStudent* stu = [[TRStudent alloc]init];
- stu.age = 18;
- stu.name = @"zhangsan";
- TRStudent* stu2 = [[TRStudent alloc]init];
- stu2.age = 20;
- stu2.name = @"lisi";
- TRStudent* stu3 = [[TRStudent alloc]init];
- stu3.age = 30;
- stu3.name = @"wangwu";
- TRStudent* stu4 = [[TRStudent alloc]init];
- stu4.age = 40;
- stu4.name = @"zhaoliu";
- TRStudent* stu5 = [[TRStudent alloc]init];
- stu5.age = 35;
- stu5.name = @"qianqi";
- NSMutableArray* students = [NSMutableArray arrayWithObjects:stu,stu2,stu3,stu4,stu5, nil];
- NSLog(@"遍历学生内容..........");
- for (int i = 0; i<[students count]; i++) {
- TRStudent* stu = [students objectAtIndex:i];
- NSLog(@"stu age:%d name:%@",stu.age,stu.name);
- }
- }
- return 0;
- }
上述代码中，以下代码：
- for (int i = 0; i<[students count]; i++) {
- TRStudent* stu = [students objectAtIndex:i];
- NSLog(@"stu age:%d name:%@",stu.age,stu.name);
- }
是设置一个循环来遍历数组。NSMutableArray类的方法count返回对象students中的数组元素个数，在这里用于限定循环的次数。NSMutableArray类的方法objectAtIndex：返回指定位置的数组元素值，实参i用于指定要返回哪个数组元素。最后，使用NSLog在控制台上输出TRStudent类对象的两个属性值。
1.3 完整代码
本案例中，类TRStudent声明，即TRStudent.h文件，完整代码如下所示：
- #import <Foundation/Foundation.h>
- @interface TRStudent : NSObject
- @property(nonatomic,assign)int age;
- @property(nonatomic,copy)NSString* name;
- @end
类TRStudent实现，即TRStudent.m文件，完整代码如下所示：
- #import "TRStudent.h"
- @implementation TRStudent
- -(NSString *)description{
- return [NSString stringWithFormat:@"age:%d",self.age];
- }
- @end
主程序，即main.m，完整代码如下所示：
- #import <Foundation/Foundation.h>
- #import "TRStudent.h"
- int main(int argc, const char * argv[])
- {
- @autoreleasepool {
- // insert code here...
- TRStudent* stu = [[TRStudent alloc]init];
- stu.age = 18;
- stu.name = @"zhangsan";
- TRStudent* stu2 = [[TRStudent alloc]init];
- stu2.age = 20;
- stu2.name = @"lisi";
- TRStudent* stu3 = [[TRStudent alloc]init];
- stu3.age = 30;
- stu3.name = @"wangwu";
- TRStudent* stu4 = [[TRStudent alloc]init];
- stu4.age = 40;
- stu4.name = @"zhaoliu";
- TRStudent* stu5 = [[TRStudent alloc]init];
- stu5.age = 35;
- stu5.name = @"qianqi";
- NSMutableArray* students = [NSMutableArray arrayWithObjects:stu,stu2,stu3,stu4,stu5, nil];
- NSLog(@"遍历学生内容..........");
- for (int i = 0; i<[students count]; i++) {
- TRStudent* stu = [students objectAtIndex:i];
- NSLog(@"stu age:%d name:%@",stu.age,stu.name);
- }
- }
- return 0;
- }
2 重构学生与学校的练习
2.1 问题
本案例要求用集合解决下述问题。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。
2.2 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Day03-2工程中新添加Book.h文件，用于定义新的类Book。
代码如下所示：
- #import <Foundation/Foundation.h>
- @interface Book : NSObject<NSCopying>
- @property(nonatomic, copy)NSString *name;
- @property(nonatomic,assign)int price;
- @end
在上述代码中，以下代码：
- @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：
- @property(nonatomic, copy)NSString *name;
- @property(nonatomic,assign)int price;
在Book类中定义了两个属性，一个是NSString类的对象name，用于存储书的名字；另一个是整型变量price，用于存储书的价格。
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：
- #import "Book.h"
- @implementation Book
- -(id)copyWithZone:(NSZone*)zone
- {
- Book* book = [[Book allocWithZone:zone] init];
- book.name = self.name;
- book.price = self.price;
- return book;
- }
- -(void)dealloc{
- NSLog(@"书对象销毁了 price:%d",self.price);
- }
- @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：
- Book* book = [[Book allocWithZone:zone] init];
- book.name = self.name;
- 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Day03-2工程中新添加TRStudent.h文件，用于定义新的类TRStudent。
代码如下所示：
- #import <Foundation/Foundation.h>
- #import "Book.h"
- @interface TRStudent : NSObject
- @property(nonatomic,assign)int age;
- @property(nonatomic,copy)NSString* name;
- @property(nonatomic,copy)Book *book;
- -(id)initWithAge:(int)age andName:(NSString*)name andBook:(Book*)book;
- +(id)studentWithAge:(int)age andName:(NSString*)name andBook:(Book*)book;
- -(void)print:(id)condition;
- @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：
- @property(nonatomic,assign) int age;
用于存储学生的年龄。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assign，对于C语言的基本数据类型，只能选取这个参数。
另一个属性是name，如下代码所示：
- @property(nonatomic,copy)NSString* name;
用于存储学生的姓名。它有两个参数，一个是nonatomic，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。
最后一个属性是book，如下代码所示：
- @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：
- -(id)initWithAge:(int)age andName:(NSString*)name andBook:(Book*)book;
- +(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：
- -(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：
- #import "TRStudent.h"
- @implementation TRStudent
- -(id)initWithAge:(int)age
- andName:(NSString*)name
- andBook:(Book*)book{
- self = [super init];
- if (self) {
- self.age = age;
- self.name = name;
- self.book = book;
- }
- return self;
- }
- +(id)studentWithAge:(int)age
- andName:(NSString*)name
- andBook:(Book*)book{
- return [[TRStudent alloc]initWithAge:age andName:name andBook:book];
- }
- -(void)print:(id)condition
- {
- bool a = [condition isKindOfClass:[NSNumber class]];
- bool b = [condition intValue] == self.age;
- bool c = [condition isKindOfClass:[NSString class]];
- bool d = [self.name isEqualToString:condition];
- if ((a && b) || (c && d))
- NSLog(@"stu name:%@, age:%d", self.name, self.age);
- }
- @end
上述代码中，以下代码：
- bool a = [condition isKindOfClass:[NSNumber class]];
- 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：
- bool c = [condition isKindOfClass:[NSString class]];
- 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：
- if ((a && b) || (c && d))
- 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：
- #import <Foundation/Foundation.h>
- #import "TRStudent.h"
- int main(int argc, const char * argv[])
- {
- @autoreleasepool {
- // insert code here...
- //创建学生对象
- Book* book1 = [[Book alloc] init];
- book1.name = @"sanguo";
- book1.price = 20;
- TRStudent* stu1 = [TRStudent studentWithAge:18 andName:@"zhangsan" andBook:book1];
- Book* book2 = [[Book alloc] init];
- book2.name = @"shuihu";
- book2.price = 18;
- TRStudent* stu2 = [TRStudent studentWithAge:19 andName:@"lisi" andBook:book2];
- Book* book3 = [[Book alloc] init];
- book3.name = @"xiyouji";
- book3.price = 28;
- TRStudent* stu3 = [TRStudent studentWithAge:20 andName:@"wangwu" andBook:book3];
- Book* book4 = [[Book alloc] init];
- book4.name = @"hongluomeng";
- book4.price = 24;
- TRStudent* stu4 = [TRStudent studentWithAge:21 andName:@"zhaoliu" andBook:book4];
- Book* book5 = [[Book alloc] init];
- book5.name = @"fengshenyanyi";
- book5.price = 22;
- TRStudent* stu5 = [TRStudent studentWithAge:22 andName:@"qianqi" andBook:book5];
- Book* book6 = [[Book alloc] init];
- book6.name = @"liaozhaizhiyi";
- book6.price = 15;
- TRStudent* stu6 = [TRStudent studentWithAge:23 andName:@"zhangfei" andBook:book6];
- Book* book7 = [[Book alloc] init];
- book7.name = @"sanxiawuyi";
- book7.price = 17;
- TRStudent* stu7 = [TRStudent studentWithAge:24 andName:@"guanyu" andBook:book7];
- Book* book8 = [[Book alloc] init];
- book8.name = @"yuefeizhuan";
- book8.price = 27;
- TRStudent* stu8 = [TRStudent studentWithAge:25 andName:@"zhaoyun" andBook:book8];
- }
- return 0;
- }
上述代码中，以下代码：
- //创建学生对象
- Book* book1 = [[Book alloc] init];
- book1.name = @"sanguo";
- book1.price = 20;
- 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集合
代码如下所示：
- #import <Foundation/Foundation.h>
- #import "TRStudent.h"
- int main(int argc, const char * argv[])
- {
- @autoreleasepool {
- // insert code here...
- //创建学生对象
- Book* book1 = [[Book alloc] init];
- book1.name = @"sanguo";
- book1.price = 20;
- TRStudent* stu1 = [TRStudent studentWithAge:18 andName:@"zhangsan" andBook:book1];
- Book* book2 = [[Book alloc] init];
- book2.name = @"shuihu";
- book2.price = 18;
- TRStudent* stu2 = [TRStudent studentWithAge:19 andName:@"lisi" andBook:book2];
- Book* book3 = [[Book alloc] init];
- book3.name = @"xiyouji";
- book3.price = 28;
- TRStudent* stu3 = [TRStudent studentWithAge:20 andName:@"wangwu" andBook:book3];
- Book* book4 = [[Book alloc] init];
- book4.name = @"hongluomeng";
- book4.price = 24;
- TRStudent* stu4 = [TRStudent studentWithAge:21 andName:@"zhaoliu" andBook:book4];
- Book* book5 = [[Book alloc] init];
- book5.name = @"fengshenyanyi";
- book5.price = 22;
- TRStudent* stu5 = [TRStudent studentWithAge:22 andName:@"qianqi" andBook:book5];
- Book* book6 = [[Book alloc] init];
- book6.name = @"liaozhaizhiyi";
- book6.price = 15;
- TRStudent* stu6 = [TRStudent studentWithAge:23 andName:@"zhangfei" andBook:book6];
- Book* book7 = [[Book alloc] init];
- book7.name = @"sanxiawuyi";
- book7.price = 17;
- TRStudent* stu7 = [TRStudent studentWithAge:24 andName:@"guanyu" andBook:book7];
- Book* book8 = [[Book alloc] init];
- book8.name = @"yuefeizhuan";
- book8.price = 27;
- TRStudent* stu8 = [TRStudent studentWithAge:25 andName:@"zhaoyun" andBook:book8];
- //班级
- NSSet* class1403A = [NSSet setWithObjects:stu1,stu2,nil];
- NSSet* class1403B = [NSSet setWithObjects:stu3,stu4,nil];
- NSSet* class1403C = [NSSet setWithObjects:stu5,stu6,nil];
- NSSet* class1403D = [NSSet setWithObjects:stu7,stu8,nil];
- }
- return 0;
- }
上述代码中，以下代码：
- //班级
- NSSet* class1403A = [NSSet setWithObjects:stu1,stu2,nil];
- NSSet* class1403B = [NSSet setWithObjects:stu3,stu4,nil];
- NSSet* class1403C = [NSSet setWithObjects:stu5,stu6,nil];
- NSSet* class1403D = [NSSet setWithObjects:stu7,stu8,nil];
创建了四个集合对象，每个集合对象为一个班级，班级中有两个学生作为集合元素。其中使用工厂方法setWithObjects创建集合对象。值得注意的是，在形参的最后是nil，它代表放入集合中的元素结束。
步骤五：在主程序中创建学院和学校
代码如下所示：
- #import <Foundation/Foundation.h>
- #import "TRStudent.h"
- int main(int argc, const char * argv[])
- {
- @autoreleasepool {
- // insert code here...
- //创建学生对象
- Book* book1 = [[Book alloc] init];
- book1.name = @"sanguo";
- book1.price = 20;
- TRStudent* stu1 = [TRStudent studentWithAge:18 andName:@"zhangsan" andBook:book1];
- Book* book2 = [[Book alloc] init];
- book2.name = @"shuihu";
- book2.price = 18;
- TRStudent* stu2 = [TRStudent studentWithAge:19 andName:@"lisi" andBook:book2];
- Book* book3 = [[Book alloc] init];
- book3.name = @"xiyouji";
- book3.price = 28;
- TRStudent* stu3 = [TRStudent studentWithAge:20 andName:@"wangwu" andBook:book3];
- Book* book4 = [[Book alloc] init];
- book4.name = @"hongluomeng";
- book4.price = 24;
- TRStudent* stu4 = [TRStudent studentWithAge:21 andName:@"zhaoliu" andBook:book4];
- Book* book5 = [[Book alloc] init];
- book5.name = @"fengshenyanyi";
- book5.price = 22;
- TRStudent* stu5 = [TRStudent studentWithAge:22 andName:@"qianqi" andBook:book5];
- Book* book6 = [[Book alloc] init];
- book6.name = @"liaozhaizhiyi";
- book6.price = 15;
- TRStudent* stu6 = [TRStudent studentWithAge:23 andName:@"zhangfei" andBook:book6];
- Book* book7 = [[Book alloc] init];
- book7.name = @"sanxiawuyi";
- book7.price = 17;
- TRStudent* stu7 = [TRStudent studentWithAge:24 andName:@"guanyu" andBook:book7];
- Book* book8 = [[Book alloc] init];
- book8.name = @"yuefeizhuan";
- book8.price = 27;
- TRStudent* stu8 = [TRStudent studentWithAge:25 andName:@"zhaoyun" andBook:book8];
- //班级
- NSSet* class1403A = [NSSet setWithObjects:stu1,stu2,nil];
- NSSet* class1403B = [NSSet setWithObjects:stu3,stu4,nil];
- NSSet* class1403C = [NSSet setWithObjects:stu5,stu6,nil];
- NSSet* class1403D = [NSSet setWithObjects:stu7,stu8,nil];
- //学院
- NSSet* college3G = [NSSet setWithObjects:class1403A,class1403B,nil];
- NSSet* collegeTest = [NSSet setWithObjects:class1403C,class1403D,nil];
- //学校
- NSSet* tarena = [NSSet setWithObjects:college3G,collegeTest,nil];
- }
- return 0;
- }
上述代码中，以下代码：
- //学院
- NSSet* college3G = [NSSet setWithObjects:class1403A,class1403B,nil];
- NSSet* collegeTest = [NSSet setWithObjects:class1403C,class1403D,nil];
- //学校
- NSSet* tarena = [NSSet setWithObjects:college3G,collegeTest,nil];
创建了两个学院集合，每个学院集合中有两个班级集合作为集合元素。还创建了一个学校集合，其中包含上述两个学院集合作为集合元素。
步骤六：在主程序中遍历输出所有学生信息
代码如下所示：
- #import <Foundation/Foundation.h>
- #import "TRStudent.h"
- int main(int argc, const char * argv[])
- {
- @autoreleasepool {
- // insert code here...
- //创建学生对象
- Book* book1 = [[Book alloc] init];
- book1.name = @"sanguo";
- book1.price = 20;
- TRStudent* stu1 = [TRStudent studentWithAge:18 andName:@"zhangsan" andBook:book1];
- Book* book2 = [[Book alloc] init];
- book2.name = @"shuihu";
- book2.price = 18;
- TRStudent* stu2 = [TRStudent studentWithAge:19 andName:@"lisi" andBook:book2];
- Book* book3 = [[Book alloc] init];
- book3.name = @"xiyouji";
- book3.price = 28;
- TRStudent* stu3 = [TRStudent studentWithAge:20 andName:@"wangwu" andBook:book3];
- Book* book4 = [[Book alloc] init];
- book4.name = @"hongluomeng";
- book4.price = 24;
- TRStudent* stu4 = [TRStudent studentWithAge:21 andName:@"zhaoliu" andBook:book4];
- Book* book5 = [[Book alloc] init];
- book5.name = @"fengshenyanyi";
- book5.price = 22;
- TRStudent* stu5 = [TRStudent studentWithAge:22 andName:@"qianqi" andBook:book5];
- Book* book6 = [[Book alloc] init];
- book6.name = @"liaozhaizhiyi";
- book6.price = 15;
- TRStudent* stu6 = [TRStudent studentWithAge:23 andName:@"zhangfei" andBook:book6];
- Book* book7 = [[Book alloc] init];
- book7.name = @"sanxiawuyi";
- book7.price = 17;
- TRStudent* stu7 = [TRStudent studentWithAge:24 andName:@"guanyu" andBook:book7];
- Book* book8 = [[Book alloc] init];
- book8.name = @"yuefeizhuan";
- book8.price = 27;
- TRStudent* stu8 = [TRStudent studentWithAge:25 andName:@"zhaoyun" andBook:book8];
- //班级
- NSSet* class1403A = [NSSet setWithObjects:stu1,stu2,nil];
- NSSet* class1403B = [NSSet setWithObjects:stu3,stu4,nil];
- NSSet* class1403C = [NSSet setWithObjects:stu5,stu6,nil];
- NSSet* class1403D = [NSSet setWithObjects:stu7,stu8,nil];
- //学院
- NSSet* college3G = [NSSet setWithObjects:class1403A,class1403B,nil];
- NSSet* collegeTest = [NSSet setWithObjects:class1403C,class1403D,nil];
- //学校
- NSSet* tarena = [NSSet setWithObjects:college3G,collegeTest,nil];
- //遍历学校
- for (NSSet* college in tarena)
- {
- //遍历学院
- for (NSSet* class in college)
- {
- //遍历班级
- for (TRStudent* stu in class)
- {
- NSLog(@"stu name:%@, age:%d", stu.name, stu.age);
- }
- }
- }
- }
- return 0;
- }
上述代码中，以下代码：
- //遍历学校
- for (NSSet* college in tarena)
- {
- //遍历学院
- for (NSSet* class in college)
- {
- //遍历班级
- for (TRStudent* stu in class)
- {
- NSLog(@"name:%@, age:%d", stu.name, stu.age);
- }
- }
- }
通过三重快速遍历方法遍历所有学生的信息。以下代码：
- //遍历学校
- for (NSSet* college in tarena)
是遍历学校tarena。每次从集合tarena中取出一个元素，放入college中，因为学校集合tarena内的元素为两个学院集合，所以college的数据类型为NSSet*。
以下代码：
- //遍历学院
- for (NSSet* class in college)
是遍历学院college。每次从集合college中取出一个元素，放入class中，因为学院集合college内的元素为两个班级集合，所以class的数据类型为NSSet*。
以下代码：
- //遍历班级
- for (TRStudent* stu in class)
是遍历班级class。因为班级集合class中是两个学生类TRStudent的对象，所以stu的数据类型为TRStudent*。
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：
- #import <Foundation/Foundation.h>
- #import "TRStudent.h"
- int main(int argc, const char * argv[])
- {
- @autoreleasepool {
- // insert code here...
- //创建学生对象
- Book* book1 = [[Book alloc] init];
- book1.name = @"sanguo";
- book1.price = 20;
- TRStudent* stu1 = [TRStudent studentWithAge:18 andName:@"zhangsan" andBook:book1];
- Book* book2 = [[Book alloc] init];
- book2.name = @"shuihu";
- book2.price = 18;
- TRStudent* stu2 = [TRStudent studentWithAge:19 andName:@"lisi" andBook:book2];
- Book* book3 = [[Book alloc] init];
- book3.name = @"xiyouji";
- book3.price = 28;
- TRStudent* stu3 = [TRStudent studentWithAge:20 andName:@"wangwu" andBook:book3];
- Book* book4 = [[Book alloc] init];
- book4.name = @"hongluomeng";
- book4.price = 24;
- TRStudent* stu4 = [TRStudent studentWithAge:21 andName:@"zhaoliu" andBook:book4];
- Book* book5 = [[Book alloc] init];
- book5.name = @"fengshenyanyi";
- book5.price = 22;
- TRStudent* stu5 = [TRStudent studentWithAge:22 andName:@"qianqi" andBook:book5];
- Book* book6 = [[Book alloc] init];
- book6.name = @"liaozhaizhiyi";
- book6.price = 15;
- TRStudent* stu6 = [TRStudent studentWithAge:23 andName:@"zhangfei" andBook:book6];
- Book* book7 = [[Book alloc] init];
- book7.name = @"sanxiawuyi";
- book7.price = 17;
- TRStudent* stu7 = [TRStudent studentWithAge:24 andName:@"guanyu" andBook:book7];
- Book* book8 = [[Book alloc] init];
- book8.name = @"yuefeizhuan";
- book8.price = 27;
- TRStudent* stu8 = [TRStudent studentWithAge:25 andName:@"zhaoyun" andBook:book8];
- //班级
- NSSet* class1403A = [NSSet setWithObjects:stu1,stu2,nil];
- NSSet* class1403B = [NSSet setWithObjects:stu3,stu4,nil];
- NSSet* class1403C = [NSSet setWithObjects:stu5,stu6,nil];
- NSSet* class1403D = [NSSet setWithObjects:stu7,stu8,nil];
- //学院
- NSSet* college3G = [NSSet setWithObjects:class1403A,class1403B,nil];
- NSSet* collegeTest = [NSSet setWithObjects:class1403C,class1403D,nil];
- //学校
- NSSet* tarena = [NSSet setWithObjects:college3G,collegeTest,nil];
- //遍历学校
- for (NSSet* college in tarena)
- {
- //遍历学院
- for (NSSet* class in college)
- {
- //遍历班级
- for (TRStudent* stu in class)
- {
- NSLog(@"name:%@, age:%d", stu.name, stu.age);
- }
- }
- }
- //遍历学校
- for (NSSet* college in tarena)
- {
- //遍历学院
- for (NSSet* class in college)
- {
- //输出年龄为18岁的学生信息
- [class makeObjectsPerformSelector:@selector(print:) withObject:[NSNumber numberWithInt:18]];
- //输出姓名为“张三”的学生信息
- [class makeObjectsPerformSelector:@selector(print:) withObject:@"zhangsan"];
- }
- }
- }
- return 0;
- }
上述代码中，以下代码：
- //输出年龄为18岁的学生信息
- [class makeObjectsPerformSelector:@selector(print:) withObject:[NSNumber numberWithInt:18]];
显示class集合中年龄为18岁的学生信息。通过向集合对象class发送NSSet类的makeObjectsPerformSelector：withObject：消息，使集合对象class中的每个元素（即TRStudent类的对象）均调用第一个实参@selector(print:)指定的TRStudent类中print方法，在控制台上输出满足条件（年龄为18岁）的学生的信息。条件（年龄为18岁）是通过makeObjectsPerformSelector：withObject：消息的第二个实参[NSNumber numberWithInt:18]传入给print方法的。
上述代码中，以下代码：
- //输出姓名为“张三”的学生信息
- [class makeObjectsPerformSelector:@selector(print:) withObject:@"zhangsan"];
显示class集合中姓名为zhangsan的学生信息。
上述代码比步骤六（输出所有学生信息）中的遍历次数少了一次，这是因为NSSet类的makeObjectsPerformSelector：withObject：消息内本身还要遍历一次，把集合class内的所有元素逐个调用一次print方法。
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：
- #import <Foundation/Foundation.h>
- #import "TRStudent.h"
- int main(int argc, const char * argv[])
- {
- @autoreleasepool {
- // insert code here...
- //创建学生对象
- Book* book1 = [[Book alloc] init];
- book1.name = @"sanguo";
- book1.price = 20;
- TRStudent* stu1 = [TRStudent studentWithAge:18 andName:@"zhangsan" andBook:book1];
- Book* book2 = [[Book alloc] init];
- book2.name = @"shuihu";
- book2.price = 18;
- TRStudent* stu2 = [TRStudent studentWithAge:19 andName:@"lisi" andBook:book2];
- Book* book3 = [[Book alloc] init];
- book3.name = @"xiyouji";
- book3.price = 28;
- TRStudent* stu3 = [TRStudent studentWithAge:20 andName:@"wangwu" andBook:book3];
- Book* book4 = [[Book alloc] init];
- book4.name = @"hongluomeng";
- book4.price = 24;
- TRStudent* stu4 = [TRStudent studentWithAge:21 andName:@"zhaoliu" andBook:book4];
- Book* book5 = [[Book alloc] init];
- book5.name = @"fengshenyanyi";
- book5.price = 22;
- TRStudent* stu5 = [TRStudent studentWithAge:22 andName:@"qianqi" andBook:book5];
- Book* book6 = [[Book alloc] init];
- book6.name = @"liaozhaizhiyi";
- book6.price = 15;
- TRStudent* stu6 = [TRStudent studentWithAge:23 andName:@"zhangfei" andBook:book6];
- Book* book7 = [[Book alloc] init];
- book7.name = @"sanxiawuyi";
- book7.price = 17;
- TRStudent* stu7 = [TRStudent studentWithAge:24 andName:@"guanyu" andBook:book7];
- Book* book8 = [[Book alloc] init];
- book8.name = @"yuefeizhuan";
- book8.price = 27;
- TRStudent* stu8 = [TRStudent studentWithAge:25 andName:@"zhaoyun" andBook:book8];
- //班级
- NSSet* class1403A = [NSSet setWithObjects:stu1,stu2,nil];
- NSSet* class1403B = [NSSet setWithObjects:stu3,stu4,nil];
- NSSet* class1403C = [NSSet setWithObjects:stu5,stu6,nil];
- NSSet* class1403D = [NSSet setWithObjects:stu7,stu8,nil];
- //学院
- NSSet* college3G = [NSSet setWithObjects:class1403A,class1403B,nil];
- NSSet* collegeTest = [NSSet setWithObjects:class1403C,class1403D,nil];
- //学校
- NSSet* tarena = [NSSet setWithObjects:college3G,collegeTest,nil];
- //遍历学校
- for (NSSet* college in tarena)
- {
- //遍历学院
- for (NSSet* class in college)
- {
- //遍历班级
- for (TRStudent* stu in class)
- {
- NSLog(@"name:%@, age:%d", stu.name, stu.age);
- }
- }
- }
- //遍历学校
- for (NSSet* college in tarena)
- {
- //遍历学院
- for (NSSet* class in college)
- {
- //输出年龄为18岁的学生信息
- [class makeObjectsPerformSelector:@selector(print:) withObject:[NSNumber numberWithInt:18]];
- //输出姓名为“张三”的学生信息
- [class makeObjectsPerformSelector:@selector(print:) withObject:@"zhangsan"];
- }
- }
- //遍历学校
- for (NSSet* college in tarena)
- {
- //遍历学院
- for (NSSet* class in college)
- {
- //遍历班级
- for (TRStudent* stu in class)
- {
- NSLog(@"book name:%@, price:%d", stu.book.name, stu.book.price);
- }
- }
- }
- }
- return 0;
- }
上述代码再一次使用了三重快速遍历，这一次与步骤六（遍历输出所有学生信息）中的三重快速遍历相比，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。
2.3 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：
- #import <Foundation/Foundation.h>
- @interface Book : NSObject<NSCopying>
- @property(nonatomic, copy)NSString *name;
- @property(nonatomic,assign)int price;
- @end
类Book实现，即Book.m文件，完整代码如下所示：
- #import "Book.h"
- @implementation Book
- -(id)copyWithZone:(NSZone*)zone
- {
- Book* book = [[Book allocWithZone:zone] init];
- book.name = self.name;
- book.price = self.price;
- return book;
- }
- -(void)dealloc{
- NSLog(@"书对象销毁了 price:%d",self.price);
- }
- @end
本案例中，类TRStudent声明，即TRStudent.h文件，完整代码如下所示：
- #import <Foundation/Foundation.h>
- #import "Book.h"
- @interface TRStudent : NSObject
- @property(nonatomic,assign)int age;
- @property(nonatomic,copy)NSString* name;
- @property(nonatomic,copy)Book *book;
- -(id)initWithAge:(int)age andName:(NSString*)name andBook:(Book*)book;
- +(id)studentWithAge:(int)age andName:(NSString*)name andBook:(Book*)book;
- -(void)print:(id)condition;
- @end
类TRStudent实现，即TRStudent.m文件，完整代码如下所示：
- #import "TRStudent.h"
- @implementation TRStudent
- -(id)initWithAge:(int)age
- andName:(NSString*)name
- andBook:(Book*)book{
- self = [super init];
- if (self) {
- self.age = age;
- self.name = name;
- self.book = book;
- }
- return self;
- }
- +(id)studentWithAge:(int)age
- andName:(NSString*)name
- andBook:(Book*)book{
- return [[TRStudent alloc]initWithAge:age andName:name andBook:book];
- }
- -(void)print:(id)condition
- {
- bool a = [condition isKindOfClass:[NSNumber class]];
- bool b = [condition intValue] == self.age;
- bool c = [condition isKindOfClass:[NSString class]];
- bool d = [self.name isEqualToString:condition];
- if ((a && b) || (c && d))
- NSLog(@"stu name:%@, age:%d", self.name, self.age);
- }
- @end
主程序，即main.m，完整代码如下所示：
- #import <Foundation/Foundation.h>
- #import "TRStudent.h"
- int main(int argc, const char * argv[])
- {
- @autoreleasepool {
- // insert code here...
- //创建学生对象
- Book* book1 = [[Book alloc] init];
- book1.name = @"sanguo";
- book1.price = 20;
- TRStudent* stu1 = [TRStudent studentWithAge:18 andName:@"zhangsan" andBook:book1];
- Book* book2 = [[Book alloc] init];
- book2.name = @"shuihu";
- book2.price = 18;
- TRStudent* stu2 = [TRStudent studentWithAge:19 andName:@"lisi" andBook:book2];
- Book* book3 = [[Book alloc] init];
- book3.name = @"xiyouji";
- book3.price = 28;
- TRStudent* stu3 = [TRStudent studentWithAge:20 andName:@"wangwu" andBook:book3];
- Book* book4 = [[Book alloc] init];
- book4.name = @"hongluomeng";
- book4.price = 24;
- TRStudent* stu4 = [TRStudent studentWithAge:21 andName:@"zhaoliu" andBook:book4];
- Book* book5 = [[Book alloc] init];
- book5.name = @"fengshenyanyi";
- book5.price = 22;
- TRStudent* stu5 = [TRStudent studentWithAge:22 andName:@"qianqi" andBook:book5];
- Book* book6 = [[Book alloc] init];
- book6.name = @"liaozhaizhiyi";
- book6.price = 15;
- TRStudent* stu6 = [TRStudent studentWithAge:23 andName:@"zhangfei" andBook:book6];
- Book* book7 = [[Book alloc] init];
- book7.name = @"sanxiawuyi";
- book7.price = 17;
- TRStudent* stu7 = [TRStudent studentWithAge:24 andName:@"guanyu" andBook:book7];
- Book* book8 = [[Book alloc] init];
- book8.name = @"yuefeizhuan";
- book8.price = 27;
- TRStudent* stu8 = [TRStudent studentWithAge:25 andName:@"zhaoyun" andBook:book8];
- //班级
- NSSet* class1403A = [NSSet setWithObjects:stu1,stu2,nil];
- NSSet* class1403B = [NSSet setWithObjects:stu3,stu4,nil];
- NSSet* class1403C = [NSSet setWithObjects:stu5,stu6,nil];
- NSSet* class1403D = [NSSet setWithObjects:stu7,stu8,nil];
- //学院
- NSSet* college3G = [NSSet setWithObjects:class1403A,class1403B,nil];
- NSSet* collegeTest = [NSSet setWithObjects:class1403C,class1403D,nil];
- //学校
- NSSet* tarena = [NSSet setWithObjects:college3G,collegeTest,nil];
- //遍历学校
- for (NSSet* college in tarena)
- {
- //遍历学院
- for (NSSet* class in college)
- {
- //遍历班级
- for (TRStudent* stu in class)
- {
- NSLog(@"stu name:%@, age:%d", stu.name, stu.age);
- }
- }
- }
- //遍历学校
- for (NSSet* college in tarena)
- {
- //遍历学院
- for (NSSet* class in college)
- {
- //输出年龄为18岁的学生信息
- [class makeObjectsPerformSelector:@selector(print:) withObject:[NSNumber numberWithInt:18]];
- //输出姓名为“张三”的学生信息
- [class makeObjectsPerformSelector:@selector(print:) withObject:@"zhangsan"];
- }
- }
- //遍历学校
- for (NSSet* college in tarena)
- {
- //遍历学院
- for (NSSet* class in college)
- {
- //遍历班级
- for (TRStudent* stu in class)
- {
- NSLog(@"book name:%@, price:%d", stu.book.name, stu.book.price);
- }
- }
- }
- }
- return 0;
- }
时间： 2024-10-02 06:45:44