本文介绍了如何排序NSMutableArray使用sortedArrayUsingDescriptors？的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！
问题描述
我有一个关于排序 NSMutableArray 的问题。我可以使用 sortedArrayUsingDescriptors：方法对对象排序数组。
例如，我有一个 NSMutableArray places 我有一个属性频率（int值），我想按照频率降序排序，但我现在不现在if
initWithKey 中输入什么？ strong> 我的对象地方包含：
NSString * name;
NSString * address;
NSString * frequency;
NSString * type;
NSMutableArray *地方;
... populate array with objects ...
NSSortDescriptor * sortByFrequency =
[[[NSSortDescriptor alloc] initWithKey：@？ ascending：NO] autorelease];
NSArray * descriptors = [NSArray arrayWithObject：sortByFrequency];
NSArray * sorted = [x sortedArrayUsingDescriptors：descriptors];
解决方案
>
- 设置
NSSortDescriptor- 使用变量的名称作为排序的设置描述符要在这些键上执行 - 使用您设置的
NSSortDescriptor获取描述符数组 - 根据这些描述符对数组进行排序
下面是两个示例，一个使用 NSDictionary 和 NSString / NSNumber 值排序 NSNumber ，另一个使用自定义类， code> NSString 字段。
按照在Cocoa编程主题中查看更多的例子和解释。
：
这样做是在GNUStep上完成的，完全相同 - 当我坐在我的Mac前面时，我会尝试：
第一个例子使用 NSString 和 NSNumber 值排序 NSNumber value： b
$ b
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];
使用描述符对频率字段进行排序 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（@\\\
Sorted ...）;
enumerator = [sortedArray objectEnumerator];
while（（obj = [enumerator nextObject]））NSLog（@％@，obj）;
OUTPUT-按频率字段排序：
2009-12-04 x [1] {address = Sydney;频率= 100。 name = Alehandro;类型= T; }
2009-12-04 x [1] {address = Melbourne;频率= 50; name = Xentro; type = X; }
2009-12-04 x [1] {address = Perth;频率= 75; name = John; type = A; }
2009-12-04 x [1] {address = Brisbane;频率= 20; name = Fjord; type = B; }
2009-12-04 x [1]
Sorted ...
2009-12-04 x [1] {address = Brisbane;频率= 20; name = Fjord; type = B; }
2009-12-04 x [1] {address = Melbourne;频率= 50; name = Xentro; type = X; }
2009-12-04 x [1] {address = Perth;频率= 75; name = John; type = A; }
2009-12-04 x [1] {address = Sydney;频率= 100; name = Alehandro; type = T; }
第二个例子是在两个 NSString 变量上使用自定义类和排序。
（参见底部的 A 类）：
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]
排序部分，按lastName排序，然后按firstName排序：
NSString * LASTNAME = @lastName;
NSString * FIRSTNAME = @firstName;
NSSortDescriptor * lastDescriptor =
[[[NSSortDescriptor alloc]
initWithKey：LASTNAME
ascending：YES
selector：@selector（localizedCaseInsensitiveCompare :)] autorelease ];
NSSortDescriptor * firstDescriptor =
[[[NSSortDescriptor alloc]
initWithKey：FIRSTNAME
升序：YES
选择器：@selector（localizedCaseInsensitiveCompare :)] autorelease ];
NSArray * descriptors =
[NSArray arrayWithObjects：lastDescriptor，firstDescriptor，nil];
NSArray * sortedArray =
[array sortedArrayUsingDescriptors：descriptors];
打印结果：
NSLog（@\\\
Sorted ...）;
enumerator = [sortedArray objectEnumerator];
while（（obj = [enumerator nextObject]））NSLog（@％@，obj）;
结果（排序前后） p>
2009-12-04 00：52：16.637 x [11375] Alehandro，Xentro，年龄：40
2009-12 -04 00：52：16.644 x约翰·史密斯年龄：30
2009-12-04 00：52：16.644 x约翰·史密斯，年龄：25
2009-12 -04 00：52：16.644 x [11375] Torro，Ola，年龄：45
2009-12-04 00：52：16.645 x [11375] Alehandro，Bento，年龄：41
2009-12 -04 00：52：16.645 x [11375] Alehandro，Axel，年龄：41
2009-12-04 00：52：16.645 x $ 113 $ b排序...
2009- 12-04 00：52：16.645 x [11375] Alehandro，Axel，年龄：41
2009-12-04 00：52：16.645 x [11375] Alehandro，Bento，年龄：41
2009- 12-04 00：52：16.645 x [11375] Torro，Ola，年龄：45
2009-12-04 00：52：16.645 x [11375] John，Smith，年龄：30
2009- 12-04 00：52：16.645 x约翰，史密斯，年龄：25
2009-12-04 00：52：16.645 x [11375] Alehandro，Xentro，年龄：40
类 A extends NSObject - 这里没有什么特别的：
#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
实施：
#import< Foundation / Foundation.h>
#importAh
@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
I have a question about sorting NSMutableArray. I can use sortedArrayUsingDescriptors: method to sort an array with objects.
For example I have an NSMutableArray of places where I have an attribute frequency (int value) and I want to sort descending on frequency but I don't now if I how to use it correctly.
What do I put as a key in initWithKey?
My object place contains:
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];
解决方案
To sort your array of objects you:
- setup
NSSortDescriptor- use names of your variables as keys to setup descriptor for sorting plus the selector to be executed on those keys - get the array of descriptors using
NSSortDescriptorthat you've setup - sort your array based on those descriptors
Here are two examples, one using NSDictionary and NSString/NSNumber values sorting on NSNumber, the other one using custom class with sorting on two NSString fields.
Follow Sorting and Filtering NSArray Objects 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 NSString and NSNumber values with sorting on NSNumber value:
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];
Sorting part using descriptors with the Frequency field which is 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 - sorted by Frequency field:
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; }
Second example with custom class and sorting on two NSString variables.
Array to sort (see class A at the bottom):
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]]];
The sorting part, sort on lastName then firstName:
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];
Print the result:
NSLog(@"\nSorted ...");
enumerator = [sortedArray objectEnumerator];
while ((obj = [enumerator nextObject])) NSLog(@"%@", obj);
Result (before and after sorting):
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
Class A extends NSObject - nothing special here:
#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
Implementation:
#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
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