使用自定义对象对NSArray进行排序

Question

在我的Xcode项目中,我有以下类:

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

地点

@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UITableViewController的子类中,有一个NSArray包含许多LDLocations的未排序对象.现在,我想根据LDAddress 的属性城市对NSArray的对象进行升序排序.

如何使用NSSortDescriptor对数组进行排序？我尝试了以下方法,但在排序数组时应用程序转储.

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

Answer 1

尝试将第一个键设为小写.

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

Answer 2

您还可以使用块对数组进行排序:

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