uitableview - NSInvalidArgumentException - 認識されないセレクターがインスタンスに送信されました

Question

次の関数を使用して、SearchDisplayController を使用して検索を実行しています

- (void)handleSearchForTerm:(NSString *)searchTerm{

[self.searchResults removeAllObjects]; // First clear the filtered array.

FMDatabase *db = [FMDatabase databaseWithPath:[Utility getDatabasePath]];


[db open];


FMResultSet *results = [db executeQuery: [NSString stringWithFormat:@"SELECT * FROM periods where (searchstartyear <= %@)  AND (searchendyear >= %@)", searchTerm, searchTerm]];

    NSMutableArray *array = [[NSMutableArray alloc] init ];
    [array removeAllObjects];
    while ([results next]) {
        Periods *searchPeriod = [[Periods alloc] init];
        searchPeriod.periodname = [results stringForColumn:@"PeriodName"];
        searchPeriod.startyear = [results stringForColumn:@"StartYear"];
        searchPeriod.endyear = [results stringForColumn:@"EndYear"];
        searchPeriod.thumb = [results stringForColumn:@"Thumb"];
        searchPeriod.childid = [results stringForColumn:@"ChildID"];
        [array addObject:searchPeriod];           
    }
    [self.searchResults addObject:array];


[db close];}    

期間はオブジェクトです

#import <UIKit/UIKit.h>

@interface Periods : NSObject

@property (nonatomic,strong) NSString *periodname;
@property (nonatomic,strong) NSString *startyear;
@property (nonatomic,strong) NSString *endyear;
@property (nonatomic,strong) NSString *thumb; 
@property (nonatomic,strong) NSString *childid;


@end

次のコードが実行されると、NSInvalidArgumentException - 認識されないセレクターがインスタンスに送信されます。

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    static NSString *CellIdentifier = @"PeriodsCell";

    UITableViewCell *cell = [self.mainTableView dequeueReusableCellWithIdentifier:CellIdentifier];
    if (cell == nil) {
        cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier];
    }

    // Configure the cell...

    if (tableView != [[self searchDisplayController] searchResultsTableView])
    {

        NSMutableArray *array = [periodsdataarray objectAtIndex:indexPath.section];
        NSMutableDictionary *dictionary = [array objectAtIndex:indexPath.row];




        UILabel *childIDLabel = (UILabel *)[cell viewWithTag:999];
        childIDLabel.text = [dictionary valueForKey:@"ChildID"];
        UILabel *titleLabel = (UILabel *)[cell viewWithTag:100];
        titleLabel.text = [dictionary valueForKey:@"PeriodName"];


        UILabel *previewLabel = (UILabel *)[cell viewWithTag:101];
        previewLabel.text = [NSString stringWithFormat:@"%@ - %@",[dictionary valueForKey:@"StartYear"],[dictionary valueForKey:@"EndYear"]];
        UIImageView *imageview = (UIImageView *)[cell viewWithTag:102];
        [imageview setImage:[UIImage imageNamed:[dictionary valueForKey:@"Thumb"]]];
    }
    else
    {
        Periods *periodcell = [self.searchResults objectAtIndex:indexPath.row];

        cell.tag = 666;
        UILabel *childIDLabel = (UILabel *)[cell viewWithTag:999];
        childIDLabel.text = periodcell.childid;
        UILabel *titleLabel = (UILabel *)[cell viewWithTag:100];
        titleLabel.text = periodcell.periodname;


        UILabel *previewLabel = (UILabel *)[cell viewWithTag:101];
        previewLabel.text = [NSString stringWithFormat:@"%@ - %@",periodcell.startyear,periodcell.endyear];
        UIImageView *imageview = (UIImageView *)[cell viewWithTag:102];
        [imageview setImage:[UIImage imageNamed:periodcell.thumb]];


    }

    return cell;
}

...そしてより具体的には、この行が実行されると:

childIDLabel.text = periodcell.childid;

私が間違っていることは何ですか？