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
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 city 对NSArray的对象进行升序排序。
如何使用NSSortDescriptor对数组进行排序? 我尝试了以下操作,但是在对数组进行排序时,应用程序会转储。
NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"Address.city" ascending:YES];
[_locations sortedArrayUsingDescriptors:@[sortDescriptor]];
答案 0 :(得分:14)
尝试将第一个键设为小写。
NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"address.city" ascending:YES];
答案 1 :(得分:14)
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];
}];
答案 2 :(得分:3)
这将允许使用多种类型进行排序。就像我们需要根据时间对电影进行排序,如果时间相等,则需要按名称排序。
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;
}];
答案 3 :(得分:1)
-(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;
}