排序NSArray的自定義對象

Question

在我的Xcode項目，我有以下類別：

地址

@interface LDAddress : NSObject{ 
    NSString *street; 
    NSString *zip; 
    NSString *city; 
    float latitude; 
    float longitude; 
} 

@property (nonatomic, retain) NSString *street; 
@property (nonatomic, retain) NSString *zip; 
@property (nonatomic, retain) NSString *city; 
@property (readwrite, assign, nonatomic) float latitude; 
@property (readwrite, assign, nonatomic) float longitude; 

@end 

位置

@interface LDLocation : NSObject{ 
    int locationId; 
    NSString *name; 
    LDAddress *address; 
} 
@property (readwrite, assign, nonatomic) int locationId; 
@property (nonatomic, retain) LDAddress *address; 
@property (nonatomic, retain) NSString *name; 

@end 

在的UITableViewController的子類，有一個包含大量LDLocations未排序對象的NSArray。現在，我想根據LDAddress的城市對NSArray的對象進行升序排序。

如何使用NSSortDescriptor對數組進行排序？ 我嘗試了以下操作，但應用程序在對數組進行排序時轉儲。

NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"Address.city" ascending:YES]; 
[_locations sortedArrayUsingDescriptors:@[sortDescriptor]]; 

Answer 1

嘗試使第一個關鍵字小寫。

NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"address.city" ascending:YES]; 

Answer 2

您也可以排序與塊的數組：

NSArray *sortedLocations = [_locations sortedArrayUsingComparator: ^(LDAddress *a1, LDAddress *a2) { 
     return [a1.city compare:a2.city]; 
    }]; 

Answer 3

這將使具有多種類型進行排序。就像我們需要根據時間對電影進行排序，如果時間相同，則需要按名稱排序。

NSArray *sortedArray = [childrenArray sortedArrayUsingComparator:^NSComparisonResult(id a, id b) { 
     NSNumber *first = [NSNumber numberWithLong:[(Movie*)a timeInMillis]]; 
     NSNumber *second = [NSNumber numberWithLong:[(Movie*)b timeInMillis]]; 
     NSComparisonResult result = [first compare:second]; 
     if(result == NSOrderedSame){ 
      result = [((NSString*)[(Movie*)a name]) compare:((NSString*)[(Movie*)b name])]; 
     } 
     return result; 
    }]; 

Answer 4

-(NSArray*)sortedWidgetList:(NSArray*)widgetList 
{ 
    NSSortDescriptor *firstDescriptor = [[NSSortDescriptor alloc] initWithKey:@"itemNum" ascending:YES]; 

    NSArray *sortDescriptors = [NSArray arrayWithObjects:firstDescriptor, nil]; 

    NSArray *sortedArray = [widgetList sortedArrayUsingDescriptors:sortDescriptors]; 

    return sortedArray; 
}