如何使用sortedArrayUsingDescriptors对NSMutableArray进行排序？

Question

我有一个关于排序的问题NSMutableArray。我可以使用sortedArrayUsingDescriptors:方法使用对象对数组进行排序。

比如我的places在那里我有一个属性frequency（int值）的NSMutableArray，我要作为排序依据frequency降，但我不知道如何正确使用它。

作为钥匙我在initWithKey上做了什么？

我的目标place包含：

NSString * name; 
NSString * address; 
NSString * frequency; 
NSString * type; 

---

NSMutableArray * places; 

... populate array with objects ... 

NSSortDescriptor * sortByFrequency = 
    [[[NSSortDescriptor alloc] initWithKey:@"????????" ascending:NO] autorelease]; 

NSArray * descriptors = [NSArray arrayWithObject:sortByFrequency]; 
NSArray * sorted = [x sortedArrayUsingDescriptors:descriptors]; 

Answer 1

下面是如何将排序一个NSMutableArray：

NSMutableArray *numberSort =[[NSMutableArray alloc] init]; 

    while ((key = [enumerator nextObject])) { 
     //(NSNumber *)integer = [key integerValue]; 
     [numberSort addObject:[NSNumber numberWithInt:[key intValue]]]; 
     // code that uses the returned key 
    } 


    NSArray *stringSort = [numberSort sortedArrayUsingSelector:@selector(compare:)]; 
    enumerator = [stringSort objectEnumerator]; 
    NSNumber *intKey; 

    NSMutableArray *backToString =[[NSMutableArray alloc] init]; 

    while ((intKey = [enumerator nextObject])) { 
     //(NSNumber *)integer = [key integerValue]; 
     [backToString addObject:[intKey stringValue]]; 
     // code that uses the returned key 

Answer 2

“密钥” 是你对象的方法（你的数组“x”）的元素，它返回你想要排序的东西。所以在这种情况下，你说你想按“频率”排序。然后，你所要做的就是使用返回频率的方法的名称作为键。

Answer 3

排序你，你的对象数组：

1. 设置NSSortDescriptor - 你的变量作为键设置描述符排序加选择使用的名称将在琴键上执行
2. 获得描述符的数组使用NSSortDescriptor你已经设置
3. 排序基于这些描述符

这里有两个例子，一个使用阵列NSDictionary和NSString/NSNumber值排序NSNumber，另一个使用自定义类与排序在两个NSString字段。

按照Sorting and Filtering NSArray Objects在Cocoa编程主题中看到更多的例子和解释。

例：

这是在GNUstep的做它应该工作一样可可 - 该代码是完全一样的 - 当我坐在我的Mac面前我会尝试：

NSString * NAME  = @"name"; 
NSString * ADDRESS = @"address"; 
NSString * FREQUENCY = @"frequency"; 
NSString * TYPE  = @"type"; 

NSMutableArray * array = [NSMutableArray array]; 

NSDictionary * dict; 

dict = [NSDictionary dictionaryWithObjectsAndKeys: 
      @"Alehandro", NAME, @"Sydney", ADDRESS, 
      [NSNumber numberWithInt:100], FREQUENCY, 
      @"T", TYPE, nil]; 
[array addObject:dict]; 

dict = [NSDictionary dictionaryWithObjectsAndKeys: 
      @"Xentro", NAME, @"Melbourne", ADDRESS, 
      [NSNumber numberWithInt:50], FREQUENCY, 
      @"X", TYPE, nil]; 
[array addObject:dict]; 

dict = [NSDictionary dictionaryWithObjectsAndKeys: 
      @"John", NAME, @"Perth", ADDRESS, 
      [NSNumber numberWithInt:75], 
      FREQUENCY, @"A", TYPE, nil]; 
[array addObject:dict]; 

dict = [NSDictionary dictionaryWithObjectsAndKeys: 
      @"Fjord", NAME, @"Brisbane", ADDRESS, 
      [NSNumber numberWithInt:20], FREQUENCY, 
      @"B", TYPE, nil]; 
[array addObject:dict]; 

：使用 NSString和 NSNumber值与 NSNumber值排序

第一示例

---

排序使用部分描述符与所述频率字段，它是NSNumber：

NSSortDescriptor * frequencyDescriptor = 
    [[[NSSortDescriptor alloc] initWithKey:FREQUENCY 
           ascending:YES] autorelease]; 

id obj; 
NSEnumerator * enumerator = [array objectEnumerator]; 
while ((obj = [enumerator nextObject])) NSLog(@"%@", obj); 

NSArray * descriptors = 
    [NSArray arrayWithObjects:frequencyDescriptor, nil]; 
NSArray * sortedArray = 
    [array sortedArrayUsingDescriptors:descriptors]; 

NSLog(@"\nSorted ..."); 

enumerator = [sortedArray objectEnumerator]; 
while ((obj = [enumerator nextObject])) NSLog(@"%@", obj); 

---

OUTPUT - 用频域来分类：

2009-12-04 x[1] {address = Sydney; frequency = 100; name = Alehandro; type = T; } 
2009-12-04 x[1] {address = Melbourne; frequency = 50; name = Xentro; type = X; } 
2009-12-04 x[1] {address = Perth; frequency = 75; name = John; type = A; } 
2009-12-04 x[1] {address = Brisbane; frequency = 20; name = Fjord; type = B; } 
2009-12-04 x[1] 
Sorted ... 
2009-12-04 x[1] {address = Brisbane; frequency = 20; name = Fjord; type = B; } 
2009-12-04 x[1] {address = Melbourne; frequency = 50; name = Xentro; type = X; } 
2009-12-04 x[1] {address = Perth; frequency = 75; name = John; type = A; } 
2009-12-04 x[1] {address = Sydney; frequency = 100; name = Alehandro; type = T; } 

---

---

第二个自定义类和对两个NSString变量进行排序的示例。

数组进行排序（见A类在底部）：

NSMutableArray * array = [NSMutableArray array]; 
[array addObject:[[A alloc] initWithFirstName:@"Alehandro" 
            lastName:@"Xentro" 
              age:[NSNumber numberWithInt:40]]]; 
[array addObject:[[A alloc] initWithFirstName:@"John" 
            lastName:@"Smith" 
              age:[NSNumber numberWithInt:30]]]; 
[array addObject:[[A alloc] initWithFirstName:@"John" 
            lastName:@"Smyth" 
              age:[NSNumber numberWithInt:25]]]; 
[array addObject:[[A alloc] initWithFirstName:@"Torro" 
            lastName:@"Ola" 
              age:[NSNumber numberWithInt:45]]]; 
[array addObject:[[A alloc] initWithFirstName:@"Alehandro" 
            lastName:@"Bento" 
              age:[NSNumber numberWithInt:41]]]; 
[array addObject:[[A alloc] initWithFirstName:@"Alehandro" 
            lastName:@"Axel" 
              age:[NSNumber numberWithInt:41]]]; 

---

分拣部，排序按LastName然后姓：

NSString * LASTNAME = @"lastName"; 
NSString * FIRSTNAME = @"firstName"; 

NSSortDescriptor *lastDescriptor = 
    [[[NSSortDescriptor alloc] 
     initWithKey:LASTNAME 
      ascending:YES 
      selector:@selector(localizedCaseInsensitiveCompare:)] autorelease]; 

NSSortDescriptor *firstDescriptor = 
    [[[NSSortDescriptor alloc] 
     initWithKey:FIRSTNAME 
      ascending:YES 
      selector:@selector(localizedCaseInsensitiveCompare:)] autorelease]; 

NSArray * descriptors = 
    [NSArray arrayWithObjects:lastDescriptor, firstDescriptor, nil]; 
NSArray * sortedArray = 
    [array sortedArrayUsingDescriptors:descriptors]; 

---

打印结果：

NSLog(@"\nSorted ..."); 

enumerator = [sortedArray objectEnumerator]; 
while ((obj = [enumerator nextObject])) NSLog(@"%@", obj); 

---

结果（前和排序后）：A延伸NSObject

2009-12-04 00:52:16.637 x[11375] Alehandro, Xentro, age:40 
2009-12-04 00:52:16.644 x[11375] John, Smith, age:30 
2009-12-04 00:52:16.644 x[11375] John, Smyth, age:25 
2009-12-04 00:52:16.644 x[11375] Torro, Ola, age:45 
2009-12-04 00:52:16.645 x[11375] Alehandro, Bento, age:41 
2009-12-04 00:52:16.645 x[11375] Alehandro, Axel, age:41 
2009-12-04 00:52:16.645 x[11375] 
Sorted ... 
2009-12-04 00:52:16.645 x[11375] Alehandro, Axel, age:41 
2009-12-04 00:52:16.645 x[11375] Alehandro, Bento, age:41 
2009-12-04 00:52:16.645 x[11375] Torro, Ola, age:45 
2009-12-04 00:52:16.645 x[11375] John, Smith, age:30 
2009-12-04 00:52:16.645 x[11375] John, Smyth, age:25 
2009-12-04 00:52:16.645 x[11375] Alehandro, Xentro, age:40 

类 - 这里没有什么特别：

#import <Foundation/Foundation.h> 

@interface A : NSObject 
{ 
    NSString * firstName; 
    NSString * lastName; 
    NSNumber * age; 
} 

- (id)initWithFirstName:(NSString*)aFirstName 
       lastName:(NSString*)aLastName 
        age:(NSNumber*)anAge; 

-(NSString*)description; 
+(NSString*)action; 

@end 

实现：

#import <Foundation/Foundation.h> 
#import "A.h" 

@implementation A 

- (id)init 
{ 
    return [self initWithFirstName:@"N/A" 
          lastName:@"N/A" 
           age:0]; 
} 

- (id)initWithFirstName:(NSString*)aFirstName 
       lastName:(NSString*)aLastName 
        age:(NSNumber*)anAge 
{ 
    self = [super init]; 
    if (!self) return nil; 

    firstName = [aFirstName copy]; 
    lastName = [aLastName copy]; 
    age = [anAge copy]; 

    return self; 
} 

- (void)dealloc 
{ 
    [firstName release]; 
    [lastName release]; 
    [age release]; 
    [super release]; 
} 

---

- (NSString *) description 
{ 
    return [NSString stringWithFormat: @"%@, %@, age:%@", 
             firstName, lastName, age]; 
} 
@end