ios - __NSCFConstantString objectAtIndex :]: unrecognized selector sent to instance

Question

-(UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
    static NSString *cellIdentifier = @"cvCell";

    [self.collect registerClass:[UICollectionViewCell class] forCellWithReuseIdentifier:@"cvCell"];

    CollectionViewCell *cell =[collectionView dequeueReusableCellWithReuseIdentifier:cellIdentifier forIndexPath:indexPath];



    NSMutableArray *data = [arr_list objectAtIndex:indexPath.section];

    NSString *cellData = [data objectAtIndex:indexPath.row];

    [cell.lbl setText:cellData];

    return cell;


}

它正在崩溃，并产生上述错误。我编译了它，它崩溃了

 NSString *cellData = [data objectAtIndex:indexPath.row];

声明。请帮助，提前致谢:)

Answer 1

检查 object obtained from array 是 string 还是 array 就像使用 isKindOfClass

这里你的对象是 NSString，你假设它是一个 NSArray

像这样修改:

 -(UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
    static NSString *cellIdentifier = @"cvCell";

    [self.collect registerClass:[UICollectionViewCell class] forCellWithReuseIdentifier:@"cvCell"];

    CollectionViewCell *cell =[collectionView dequeueReusableCellWithReuseIdentifier:cellIdentifier forIndexPath:indexPath];

    id data = [arr_list objectAtIndex:indexPath.section];
    NSMutableArray *arrData = nil;
    if([data isKindOfClass:[NSString class]])
       NSLog(@"its string");
    else if([data isKindOfClass:[NSMutableArray class]])
    {
       arrData = (NSMutableArray *)data;
    }
    else
    {
       NSLog(@"its something else %@",data);
    }

    NSString *cellData = @"";
    if(arrData)
       cellData = [arrData objectAtIndex:indexPath.row];

    [cell.lbl setText:cellData];

    return cell;
}