NSArray 与 NSMutableArray 的排序

　　由于集合的使用过程中，经常需要对数组进行排序操作，此博客用于总结对在OC中对数组排序的几种方法

1.当数组中存放的是Foundation框架中提供的对象时，直接使用 compare:方法

  如：NSString、NSMutableSting等

　

 1         //使用块对数组排序

 2         NSArray* arr = @[@"4",@"3",@"1",@"2"];

 3         NSMutableArray* mutArr = [arr mutableCopy];

 4         

 5         //可变数组使用块 sortUsingComparator

 6         [mutArr sortUsingComparator:^NSComparisonResult(id obj1, id obj2) {

 7             return [obj1 compare: obj2];

 8         }];

 9         //不可变数组使用Comparator排序

10         NSArray* sorted = [arr sortedArrayUsingComparator:^NSComparisonResult(id obj1, id obj2) {

11             return [obj2 compare: obj1];

12         }];

13         

14         NSLog(@"%@", sorted);

15          NSLog(@"%@", mutArr);

16 

17         //使用块对数组进行排序

18         //可变数组使用selector排序

19         NSLog(@"%@", [arr sortedArrayUsingSelector:@selector(compare:)]);

2. 当数组中存放的是自定义对象时，需要自己写排序方法，或使用NSSortDescriptor进行排序

举个例子，自定义一个Student类，生成很多Student对象，放入数组中，对数组进行排序。

   2.1 Student类

 1 #import <Foundation/Foundation.h>

 2 @class Grade;

 3 @interface Student : NSObject

 4 @property (copy, nonatomic) NSString* name;

 5 @property (assign, nonatomic) NSInteger age;

 6 @property (copy, nonatomic) NSString* stuNo;

 7 @property (strong, nonatomic) Grade* grade;

 8 - (NSComparisonResult)compare:(Student *)stu;

 9 

10 - (NSString *)description;

11 

12 @end

13 

14 @implementation Student

15 - (NSComparisonResult)compare:(Student *)stu

16 {

17     return [_name compare: [stu name]];

18 }

19 - (NSString *)description

20 {

21     return [NSString stringWithFormat:@"%@", _name];

22 }

23 @end

 2.2 排序 （使用自定义方法）

 1 //对自定义对象进行排序

 2         Grade* grade1 = [[Grade alloc] init];

 3         grade1.name = @"1023";

 4         Grade* grade2 = [[Grade alloc] init];

 5         grade2.name = @"1024";

 6         

 7         Student* stu1 = [[Student alloc] init];

 8         stu1.name = @"悟空";

 9         stu1.stuNo = @"008";

10         stu1.age = 10;

11         stu1.grade = grade1;

12         Student* stu2 = [[Student alloc] init];

13         stu2.name = @"八戒";

14         stu2.stuNo = @"007";

15         stu2.age = 12;

16         stu2.grade = grade2;

17         Student* stu3 = [[Student alloc] init];

18         stu3.name = @"唐僧";

19         stu3.stuNo = @"009";

20         stu3.age = 14;

21         stu3.grade = grade2;

22         Student* stu4 = [[Student alloc] init];

23         stu4.name = @"玉帝";

24         stu4.stuNo = @"011";

25         stu4.age = 16;

26         stu4.grade = grade1;

27         Student* stu5 = [[Student alloc] init];

28         stu5.name = @"观音";

29         stu5.stuNo = @"112";

30         stu5.age = 14;

31         stu5.grade = grade1;

32         

33         NSArray* students = @[stu1, stu2, stu3, stu4,stu5];

34         //对自定义对象排序需要自定义排序方法

35         NSArray* orderedArr = [students sortedArrayUsingSelector:@selector(compare:)];

36 //        NSLog(@"%@", orderedArr);

37         for (Student *new in orderedArr) {

38             NSLog(@"%@", new.name);

39         }

 3.使用NSSortDescriptor进行排序，NSSortDescriptor排序更多的用于多条件排序

　　使用步骤：

　　1>创建NSSortDescriptor对象

1 　　　　　//使用NSSortDescriptor对象描述某一条属性的比较规则

2         //第一个参数，是要比较的属性所对应的成员变量的名字

3         //第二个参数，指定为YES, 表示为升序，指定为NO,表示为降序

4         

5         NSSortDescriptor* desc1 = [[NSSortDescriptor alloc] initWithKey:@"_stuNo" ascending:YES];

6         NSSortDescriptor* desc2 = [[NSSortDescriptor alloc] initWithKey:@"_age" ascending:YES];

7         NSSortDescriptor* desc3 = [[NSSortDescriptor alloc] initWithKey:@"_name" ascending:YES];

8         //【注】NSSortDescriptor 支持路径，_grade为student对象的属性对象，name为_grade的属性

9         NSSortDescriptor* desc4 = [[NSSortDescriptor alloc] initWithKey:@"_grade.name" ascending:YES];

 

　　2>将NSSortDescriptor对象放入数组

1 NSArray* descArr = [NSArray arrayWithObjects: desc4,desc1, desc3, desc2, nil];

　　3>需要排序的数组调用  sortedArrayUsingDescriptors：方法进行排序

1 NSArray* sortedByDescriptor = [students sortedArrayUsingDescriptors: descArr];

　　实例代码如下：

　　Student.h文件

 1 #import <Foundation/Foundation.h>

 2 @class Grade;

 3 @interface Student : NSObject

 4 @property (copy, nonatomic) NSString* name;

 5 @property (assign, nonatomic) NSInteger age;

 6 @property (copy, nonatomic) NSString* stuNo;

 7 @property (strong, nonatomic) Grade* grade;

 8 - (NSComparisonResult)compare:(Student *)stu;

 9 

10 - (NSString *)description;

11 

12 @end

　　Student.m文件

 1 #import "Student.h"

 2 

 3 @implementation Student

 4 - (NSComparisonResult)compare:(Student *)stu

 5 {

 6     return [_name compare: [stu name]];

 7 }

 8 - (NSString *)description

 9 {

10     return [NSString stringWithFormat:@"%@", _name];

11 }

12 @end

　　Grade.h文件

1 #import <Foundation/Foundation.h>

2 

3 @interface Grade : NSObject

4 @property (copy, nonatomic) NSString* name;

5 @end

　　Grade.m文件

　　

1 #import "Grade.h"

2 

3 @implementation Grade

4 

5 @end

　　主函数：

 1 //对自定义对象进行排序

 2         Grade* grade1 = [[Grade alloc] init];

 3         grade1.name = @"1023";

 4         Grade* grade2 = [[Grade alloc] init];

 5         grade2.name = @"1024";

 6         

 7         Student* stu1 = [[Student alloc] init];

 8         stu1.name = @"悟空";

 9         stu1.stuNo = @"008";

10         stu1.age = 10;

11         stu1.grade = grade1;

12         Student* stu2 = [[Student alloc] init];

13         stu2.name = @"八戒";

14         stu2.stuNo = @"007";

15         stu2.age = 12;

16         stu2.grade = grade2;

17         Student* stu3 = [[Student alloc] init];

18         stu3.name = @"唐僧";

19         stu3.stuNo = @"009";

20         stu3.age = 14;

21         stu3.grade = grade2;

22         Student* stu4 = [[Student alloc] init];

23         stu4.name = @"玉帝";

24         stu4.stuNo = @"011";

25         stu4.age = 16;

26         stu4.grade = grade1;

27         Student* stu5 = [[Student alloc] init];

28         stu5.name = @"观音";

29         stu5.stuNo = @"112";

30         stu5.age = 14;

31         stu5.grade = grade1;

32         

33         NSArray* students = @[stu1, stu2, stu3, stu4,stu5];

34 

35 NSSortDescriptor* desc1 = [[NSSortDescriptor alloc] initWithKey:@"_stuNo" ascending:YES];

36         NSSortDescriptor* desc2 = [[NSSortDescriptor alloc] initWithKey:@"_age" ascending:YES];

37         NSSortDescriptor* desc3 = [[NSSortDescriptor alloc] initWithKey:@"_name" ascending:YES];

38         //可向下传递

39         NSSortDescriptor* desc4 = [[NSSortDescriptor alloc] initWithKey:@"_grade.name" ascending:YES];

40         NSArray* descArr = [NSArray arrayWithObjects: desc4,desc1, desc3, desc2, nil];

41 //        NSArray* descArr = [NSArray arrayWithObjects:desc4, nil];

42         NSArray* sortedByDescriptor = [students sortedArrayUsingDescriptors: descArr];

43         

44         for (Student *new in sortedByDescriptor) {

45             NSLog(@"%@", new.grade.name);

46         }