16.Object－C－－NSArray数组的排序

今天我来总结一下NSArray数组的排序方式。

NSArray数组的排序有三种方式：

1、简单排序（sortedArrayUsingSelector:）

2、利用block语法（sortedArrayUsingComparator:）

3、高级排序（sortedArrayUsingDescriptors:）

1、简单排序（sortedArrayUsingSelector:）

如果只是对字符串的排序，可以利用sortedArrayUsingSelector:方法就可以了，代码如下：

 #pragma mark 数组排序 sortedArrayUsingSelector

 void arraySort1()
 {
     NSArray *array = [NSArray arrayWithObjects:@"",@"",@"",@"",nil];
     //返回一个排好序的数组，原来的数组不会变 （SEL）中传递的是排序的规则。@selector(compare:)
     //制定元素的比较方法 compare
     NSArray *arrayNew = [array sortedArrayUsingSelector:@selector(compare:)];
     NSLog(@"arrayNew :%@",arrayNew);
 }

这里是制定使用Compare方法进行排序。我们也可以制定自己的排序方法

 #import <Foundation/Foundation.h>
 @class Book;
 @interface Student : NSObject
 @property(nonatomic,retain)NSString *firstName;
 @property(nonatomic,retain)NSString *lastName;
 @property(nonatomic,retain)Book *book;
 //快速创建student
 + (id)studentWithFirstName:(NSString*)firstName lastName:(NSString*)lastName;
 //比较规则
 - (NSComparisonResult)compareStudent:(Student*)stu;
 @end

 #import "Student.h"
 #import "Book.h"
 @implementation Student
 + (id)studentWithFirstName:(NSString*)firstName lastName:(NSString*)lastName
 {
     //类方法自动释放所以使用autorelease
     Student *stu = [[[Student alloc]init]autorelease];
     stu.firstName = firstName;
     stu.lastName = lastName;
     return stu;
 }

 - (NSComparisonResult)compareStudent:(Student*)stu
 {
     //1.先按照姓排序
     NSComparisonResult result = [self.lastName compare:stu.lastName];

     if(result == NSOrderedSame)
     {
         result = [self.firstName compare:stu.firstName];
     }
     return result;
 }
 - (NSString *)description
 {
     return  [NSString stringWithFormat:@"[%@ %@]",self.lastName,self.firstName];
 }

 - (void)dealloc
 {
     [_book release];
     [_firstName release];
     [_lastName release];
     [super dealloc];
 }
 @end

 #pragma mark 数组排序 arraySort2
 void arraySort2()
 {
     Student *stu = [Student studentWithFirstName:@"QY" lastName:@"Ma"];
     Student *stu1 = [Student studentWithFirstName:@"jf" lastName:@"Jia"];
     Student *stu2 = [Student studentWithFirstName:@"sy" lastName:@"Qu"];
     NSArray *array = [NSArray arrayWithObjects:stu,stu1,stu2,nil];
     //指定排序的方法
     NSArray *arrayNew = [array sortedArrayUsingSelector:@selector(compareStudent:)];
     NSLog(@"arrayNew : %@",arrayNew);

 }

2.利用block语法（sortedArrayUsingComparator:）

这是苹果官方提供的block方法，其中数组排序可以用sortedArrayUsingComparator:方法

 void arraySort3()
 {
     Student *stu = [Student studentWithFirstName:@"QY" lastName:@"Ma"];
     Student *stu1 = [Student studentWithFirstName:@"jf" lastName:@"Jia"];
     Student *stu2 = [Student studentWithFirstName:@"sy" lastName:@"Qu"];
     NSArray *array = [NSArray arrayWithObjects:stu,stu1,stu2,nil];
     //利用block进行排序
     NSArray *arrayNew =   [array sortedArrayUsingComparator:^NSComparisonResult(Student *obj1, Student *obj2) {
         //1.先按照姓排序
         NSComparisonResult result = [obj1.lastName compare:obj2.lastName];

         if(result == NSOrderedSame)
         {
             result = [obj1.firstName compare:obj2.firstName];
         }
         return result;
     }];
     NSLog(@"arrayNew : %@",arrayNew);
 }

3.高级排序（sortedArrayUsingDescriptors:）

如果是这样一种情况呢？Student类里有另外一个类的变量，比如说Student类除了lastName，firstName变量，还有一本书，Book类里有个name属性。对Student对象进行排序，有这样的要求：按照Book的name排序，如果是同一本书，那么再按照lastName进行排序，如果lastName也相同，最后按照firstName进行排序。

代码如下：

 //Book
 #import <Foundation/Foundation.h>

 @interface Book : NSObject
 @property(nonatomic,retain)NSString *name;
 + (id)bookWithName:(NSString*)name;
 @end

 #import "Book.h"

 @implementation Book
 + (id)bookWithName:(NSString*)name
 {
     Book *book = [[[Book alloc]init]autorelease];
     book.name = name;
     return book;

 }
 - (void)dealloc
 {
     [_name release];
     [super dealloc];
 }
 @end

 //Student
 #import <Foundation/Foundation.h>
 @class Book;
 @interface Student : NSObject
 @property(nonatomic,retain)NSString *firstName;
 @property(nonatomic,retain)NSString *lastName;
 @property(nonatomic,retain)Book *book;
 //快速创建student
 + (id)studentWithFirstName:(NSString*)firstName lastName:(NSString*)lastName;
 //快速创建student
 + (id)studentWithFirstName:(NSString*)firstName lastName:(NSString*)lastName bookName:(NSString*)bookName;
 //比较规则
 - (NSComparisonResult)compareStudent:(Student*)stu;
 @end

 #import "Student.h"
 #import "Book.h"
 @implementation Student
 + (id)studentWithFirstName:(NSString*)firstName lastName:(NSString*)lastName
 {
     //类方法自动释放所以使用autorelease
     Student *stu = [[[Student alloc]init]autorelease];
     stu.firstName = firstName;
     stu.lastName = lastName;
     return stu;
 }

 //快速创建student
 + (id)studentWithFirstName:(NSString*)firstName lastName:(NSString*)lastName bookName:(NSString*)bookName
 {
     Student *stu = [Student studentWithFirstName:firstName lastName:lastName];
     stu.book = [Book bookWithName:bookName];
     return stu;    

 }
 - (NSComparisonResult)compareStudent:(Student*)stu
 {
     //1.先按照姓排序
     NSComparisonResult result = [self.lastName compare:stu.lastName];

     if(result == NSOrderedSame)
     {
         result = [self.firstName compare:stu.firstName];
     }
     return result;
 }
 - (NSString *)description
 {
     return  [NSString stringWithFormat:@"[%@ %@ %@]",self.lastName,self.firstName,self.book.name];
 }

 - (void)dealloc
 {
     [_book release];
     [_firstName release];
     [_lastName release];
     [super dealloc];
 }
 @end

 //将排序描述按照顺序存入到数组中
 #pragma mark 数组排序 sortedArrayUsingDescriptors 排序描述器
 void arraySort5()
 {
     Student *stu1 = [Student studentWithFirstName:@"QY" lastName:@"Ma" bookName:@"book3"];
     Student *stu2 = [Student studentWithFirstName:@"JF" lastName:@"Jia" bookName:@"book1"];
     Student *stu3 = [Student studentWithFirstName:@"SY" lastName:@"Qu" bookName:@"book4"];
     NSArray *array = [NSArray arrayWithObjects:stu1,stu2,stu3, nil];
     //放入到描述器里面
     NSSortDescriptor *bookNameDesc = [NSSortDescriptor sortDescriptorWithKey:@"book.name" ascending:YES];
     NSSortDescriptor *lastNameDesc = [NSSortDescriptor sortDescriptorWithKey:@"lastName" ascending:YES];
     NSSortDescriptor *firstName = [NSSortDescriptor sortDescriptorWithKey:@"firstName" ascending:YES];
     NSArray *array1 = [NSArray arrayWithObjects:bookNameDesc,lastNameDesc,firstName,nil];
     NSArray *arrayNew = [array sortedArrayUsingDescriptors:array1];
     NSLog(@"arrayNew :%@",arrayNew);

 }