如何使用sortedArrayUsingDescriptors對NSMutableArray進行排序？我有一個關于排序的問題NSMutableArray。我可以使用sortedArrayUsingDescriptors:方法用對象對數組進行排序。比如我有一個NSMutableArray的places，我有一個屬性frequency（int值），我想降序排序上frequency，但我不知道如何正確使用它。我把什么作為鑰匙initWithKey？我的對象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];
3 回答
慕神8447489
TA貢獻1780條經驗 獲得超1個贊
要對您的對象數組進行排序：
setup
NSSortDescriptor- 使用變量名作為設置描述符進行排序的鍵以及要在這些鍵上執行的選擇器使用
NSSortDescriptor您設置的描述符數組根據這些描述符對數組進行排序
這里有兩個例子，一個使用NSDictionary和NSString/NSNumber值排序NSNumber，另一個使用自定義類，在兩個NSString字段上排序。
在Cocoa編程主題中按照排序和過濾NSArray對象來查看更多示例和說明。
示例：
這是在GNUStep上完成的，它應該在Cocoa上運行相同 - 代碼完全一樣 - 當我坐在我的Mac前面時我會嘗試：
第一個示例使用NSString和NSNumber值對值進行排序NSNumber：
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];
使用帶有頻率字段的描述符對部件進行排序，即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);
輸出 - 按頻率字段排序：
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; }第二個示例使用自定義類并對兩個NSString變量進行排序。
要排序的數組（參見A底部的類）：
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，在lastName上排序，然后是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];
打印結果：
NSLog(@"\nSorted ...");enumerator = [sortedArray objectEnumerator];while ((obj = [enumerator nextObject])) NSLog(@"%@", obj);
結果（排序前后）：
2009-12-04 00:52:16.637 x[11375] Alehandro, Xentro, age:402009-12-04 00:52:16.644 x[11375] John, Smith, age:302009-12-04 00:52:16.644 x[11375] John, Smyth, age:252009-12-04 00:52:16.644 x[11375] Torro, Ola, age:452009-12-04 00:52:16.645 x[11375] Alehandro, Bento, age:412009-12-04 00:52:16.645 x[11375] Alehandro, Axel, age:412009-12-04 00:52:16.645 x[11375]Sorted ...2009-12-04 00:52:16.645 x[11375] Alehandro, Axel, age:412009-12-04 00:52:16.645 x[11375] Alehandro, Bento, age:412009-12-04 00:52:16.645 x[11375] Torro, Ola, age:452009-12-04 00:52:16.645 x[11375] John, Smith, age:302009-12-04 00:52:16.645 x[11375] John, Smyth, age:252009-12-04 00:52:16.645 x[11375] Alehandro, Xentro, age:40
課程A延伸NSObject- 這里沒什么特別的：
#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執行：
#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
慕尼黑8549860
TA貢獻1818條經驗 獲得超11個贊
“鍵”是對象的方法（數組“x”的元素），它返回要排序的對象。所以在這種情況下，你說你想按“頻率”排序。然后，您所要做的就是使用返回頻率的方法的名稱作為鍵。
慕虎7371278
TA貢獻1802條經驗 獲得超4個贊
以下是對NSMutableArray進行排序的方法：
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- 3 回答
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