blocks|key|2734477|text|下面是如何对NSMutableArray进行排序的方法：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2734478|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+|code-block|syntax|javascript|2734479|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Here's how a would sort an NSMutableArray:

<pre><code>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 
</code></pre>

blocks|key|2734489|text|"key“是对象的一个方法(数组”x“中的元素)，它返回要排序的内容。所以在这个例子中，你说你想按“频率”排序。然后，您要做的就是使用返回频率的方法的名称作为键。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2734490|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

The "key" is a method of your objects (the elements of your array "x") that returns the thing you want to sort by. So in this case, you said that you want to sort by the "frequency". Then all you have to do is use the name of the method that returns the frequency, as the key.

blocks|key|2734533|text|若要对对象数组进行排序，请执行以下操作：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2734534|安装NSSortDescriptor+-使用变量的名称作为设置描述符的键，用于排序，再加上要在这些键上执行的选择器。|ordered-list-item|offset|length|style|CODE|2734535|使用您设置的NSSortDescriptor获取描述符数组|2734536|根据这些描述符对数组进行排序|2734537|这里有两个示例，一个使用NSDictionary和NSString/NSNumber值在NSNumber上排序，另一个使用自定义类对两个NSString字段进行排序。|2734538|遵循Cocoa编程主题中的对NSArray对象进行排序和过滤，查看更多的示例和解释。|2734539|示例|BOLD|2734540|这是在GNUStep上完成的，它在Cocoa上的工作应该是一样的--代码完全相同--当我坐在Mac前面时，我会尝试：|2734541|使用NSString+和+NSNumber+值对+NSNumber+值进行排序的第一个示例：|2734542|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];|code-block|syntax|javascript|2734543|使用描述符和频率场(+NSNumber+)对零件排序|2734544|NSSortDescriptor+*+frequencyDescriptor+=
++++[[[NSSortDescriptor+alloc]+initWithKey:FREQUENCY
+++++++++++++++++++++++++++++++++ascending:YES]+autorelease];

id+obj;
NSEnumerator+*+enumerator+=+[array+objectEnumerator];
while+((obj+=+[enumerator+nextObject]))+NSLog(@"%25@",+obj);

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

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

enumerator+=+[sortedArray+objectEnumerator];
while+((obj+=+[enumerator+nextObject]))+NSLog(@"%25@",+obj);|2734545|输出-按频率场排序：|2734546|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;+}|2734547|带有自定义类并对两个NSString+变量进行排序的第二个示例。|2734548|数组进行排序(请参见底部的类A+)：|2734549|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]]];|2734550|排序部分，在lastName上排序，然后在firstName上排序：|2734551|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];|2734552|打印结果：|2734553|NSLog(@"\nSorted+...");

enumerator+=+[sortedArray+objectEnumerator];
while+((obj+=+[enumerator+nextObject]))+NSLog(@"%25@",+obj);|2734554|结果(排序前后)：|2734555|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|2734556|类A扩展了NSObject+-在这里没有什么特别的：|2734557|#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;
%2B(NSString*)action;

@end|2734558|执行情况：|2734559|#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];
}|2734560|-+(NSString+*)+description
{
++++return+[NSString+stringWithFormat:+@"%25@,+%25@,+age:%25@",
+++++++++++++++++++++++++++++++++++++++firstName,+lastName,+age];
}
@end|2734561|entityMap|0|LINK|mutability|MUTABLE|url|http://developer.apple.com/library/mac/#documentation/Cocoa/Conceptual/Collections/Articles/index.html^0|0|2|G|0|6|G|0|0|C|C|P|H|18|8|1W|8|0|D|H|0|0|0|2|0|0|2|8|B|1|D|8|M|2|P|8|Y|C|2|8|D|8|P|8|0|0|0|Q|B|8|0|0|0|A|0|0|0|I|J|D|A|8|0|0|I|E|1|0|0|0|Y|0|0|0|5|0|0|0|9|0|0|0|Q|1|1|5|8|0|0|0|5|0|0|0^^$0|@$1|2|3|4|5|6|7|2A|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|2B|8|@$E|2C|F|2D|G|H]]|9|@]|A|$]]|$1|I|3|J|5|D|7|2E|8|@$E|2F|F|2G|G|H]]|9|@]|A|$]]|$1|K|3|L|5|D|7|2H|8|@]|9|@]|A|$]]|$1|M|3|N|5|6|7|2I|8|@$E|2J|F|2K|G|H]|$E|2L|F|2M|G|H]|$E|2N|F|2O|G|H]|$E|2P|F|2Q|G|H]]|9|@]|A|$]]|$1|O|3|P|5|6|7|2R|8|@]|9|@$E|2S|F|2T|1|2U]]|A|$]]|$1|Q|3|R|5|6|7|2V|8|@$E|2W|F|2X|G|S]]|9|@]|A|$]]|$1|T|3|U|5|6|7|2Y|8|@]|9|@]|A|$]]|$1|V|3|W|5|6|7|2Z|8|@$E|30|F|31|G|S]|$E|32|F|33|G|S]|$E|34|F|35|G|S]|$E|36|F|37|G|S]|$E|38|F|39|G|S]|$E|3A|F|3B|G|S]|$E|3C|F|3D|G|H]|$E|3E|F|3F|G|H]|$E|3G|F|3H|G|H]]|9|@]|A|$]]|$1|X|3|Y|5|Z|7|3I|8|@]|9|@]|A|$10|11]]|$1|12|3|13|5|6|7|3J|8|@$E|3K|F|3L|G|S]|$E|3M|F|3N|G|H]]|9|@]|A|$]]|$1|14|3|15|5|Z|7|3O|8|@]|9|@]|A|$10|11]]|$1|16|3|17|5|6|7|3P|8|@$E|3Q|F|3R|G|S]]|9|@]|A|$]]|$1|18|3|19|5|Z|7|3S|8|@]|9|@]|A|$10|11]]|$1|1A|3|1B|5|6|7|3T|8|@$E|3U|F|3V|G|S]|$E|3W|F|3X|G|S]|$E|3Y|F|3Z|G|H]]|9|@]|A|$]]|$1|1C|3|1D|5|6|7|40|8|@$E|41|F|42|G|S]|$E|43|F|44|G|H]]|9|@]|A|$]]|$1|1E|3|1F|5|Z|7|45|8|@]|9|@]|A|$10|11]]|$1|1G|3|1H|5|6|7|46|8|@$E|47|F|48|G|S]]|9|@]|A|$]]|$1|1I|3|1J|5|Z|7|49|8|@]|9|@]|A|$10|11]]|$1|1K|3|1L|5|6|7|4A|8|@$E|4B|F|4C|G|S]]|9|@]|A|$]]|$1|1M|3|1N|5|Z|7|4D|8|@]|9|@]|A|$10|11]]|$1|1O|3|1P|5|6|7|4E|8|@$E|4F|F|4G|G|S]]|9|@]|A|$]]|$1|1Q|3|1R|5|Z|7|4H|8|@]|9|@]|A|$10|11]]|$1|1S|3|1T|5|6|7|4I|8|@$E|4J|F|4K|G|S]|$E|4L|F|4M|G|H]|$E|4N|F|4O|G|H]]|9|@]|A|$]]|$1|1U|3|1V|5|Z|7|4P|8|@]|9|@]|A|$10|11]]|$1|1W|3|1X|5|6|7|4Q|8|@$E|4R|F|4S|G|S]]|9|@]|A|$]]|$1|1Y|3|1Z|5|Z|7|4T|8|@]|9|@]|A|$10|11]]|$1|20|3|21|5|Z|7|4U|8|@]|9|@]|A|$10|11]]|$1|22|3|-4|5|6|7|4V|8|@]|9|@]|A|$]]]|23|$24|$5|25|26|27|A|$28|29]]]]

To sort your array of objects you:

<ol>
<li>setup <code>NSSortDescriptor</code> - use names of your variables as keys to setup descriptor for sorting plus the selector to be executed on those keys</li>
<li>get the array of descriptors using <code>NSSortDescriptor</code> that you've setup</li>
<li>sort your array based on those descriptors</li>
</ol>

Here are two examples, one using <code>NSDictionary</code> and <code>NSString/NSNumber</code> values sorting on <code>NSNumber</code>, the other one using custom class with sorting on two <code>NSString</code> fields.

Follow <a href="http://developer.apple.com/library/mac/#documentation/Cocoa/Conceptual/Collections/Articles/index.html" rel="noreferrer">Sorting and Filtering NSArray Objects</a> in Cocoa programming topics to see more examples and explanation.

Example:

This was done on GNUStep it should work the same on Cocoa - the code is exactly the same - I'll try when I sit in front of my Mac:

First example using <code>NSString</code> and <code>NSNumber</code> values with sorting on <code>NSNumber</code> value:

<pre><code>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];
</code></pre>

<hr>

Sorting part using descriptors with the Frequency field which is <code>NSNumber</code>:

<pre><code>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);
</code></pre>

<hr>

OUTPUT - sorted by Frequency field:

<pre><code>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; }
</code></pre>

<hr>

<hr>

Second example with custom class and sorting on two <code>NSString</code> variables.

Array to sort (see class <code>A</code> at the bottom):

<pre><code>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]]];
</code></pre>

<hr>

The sorting part, sort on lastName then firstName:

<pre><code>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];
</code></pre>

<hr>

Print the result:

<pre><code>NSLog(@"\nSorted ...");

enumerator = [sortedArray objectEnumerator];
while ((obj = [enumerator nextObject])) NSLog(@"%@", obj);
</code></pre>

<hr>

Result (before and after sorting):

<pre><code>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
</code></pre>

Class <code>A</code> extends <code>NSObject</code> - nothing special here:

<pre><code>#import &lt;Foundation/Foundation.h&gt;

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

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

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

@end
</code></pre>

Implementation:

<pre><code>#import &lt;Foundation/Foundation.h&gt;
#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];
}
</code></pre>

<hr>

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

I have a question about sorting <code>NSMutableArray</code>. I can use <code>sortedArrayUsingDescriptors:</code> method to sort an array with objects. 

For example I have an <code>NSMutableArray</code> of <code>places</code> where I have an attribute <code>frequency</code> (int value) and I want to sort descending on <code>frequency</code> but I don't know how to use it correctly.

What do I put as a key in <code>initWithKey</code>?

My object <code>place</code> contains:

<pre><code>NSString * name;
NSString * address;
NSString * frequency;
NSString * type;
</code></pre>

<hr>

<pre><code>NSMutableArray * places;

... populate array with objects ...

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

NSArray * descriptors = [NSArray arrayWithObject:sortByFrequency];
NSArray * sorted = [x sortedArrayUsingDescriptors:descriptors];
</code></pre>

How to sort NSMutableArray using sortedArrayUsingDescriptors?

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

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我有一个关于NSMutableArray排序的问题。我可以使用sortedArrayUsingDescriptors:方法对带有对象的数组进行排序。例如，我有一个属性NSMutableArray of places，其中有一个属性frequency (int值)，我想在frequency上排序，但是我不知道如何正确地使...

问如何使用NSMutableArray对sortedArrayUsingDescriptors进行排序？
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问如何使用NSMutableArray对sortedArrayUsingDescriptors进行排序？EN