CODEWITHSUNDEEP
iosobjective-c
mvasco
mvasco

Reputation: 5101

Exception thrown if string is null

I am getting an exception if a string is null:

Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[NSNull length]: unrecognized selector sent to instance

This is one of the objects of the dictionary,that contains a null string:

{
    cabdriver = "<null>";
    code = SV1000000079;
    date = "2015-03-15";
    destiny = "";
    email = "[email protected]";
    origin = vxd;
}

And this is my code where the exception is thrown:

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    HistorialCellTableViewCell *cell = (HistorialCellTableViewCell *)[tableView dequeueReusableCellWithIdentifier:@"Cell"];

    NSString *origin = [[historialServicios objectAtIndex:indexPath.row] valueForKey:@"origin"];
    if (origin.length ==0){
        cell.origen_label.text = @"-";
    } else {
        cell.origen_label.text = origin;
    }

    NSString *destiny = [[historialServicios objectAtIndex:indexPath.row] valueForKey:@"destiny"];
    if (destiny.length ==0){
        cell.destiny_label.text = @"-";
    } else { 
        cell.destiny_label.text = destiny;
    }


    NSString *cabdriver = [[historialServicios objectAtIndex:indexPath.row] valueForKey:@"cabdriver"];
    if (cabdriver.length ==0){
        cell.conductor_label.text = @"-";
    } else {
        cell.conductor_label.text = cabdriver;
    }

    NSString *date = [[historialServicios objectAtIndex:indexPath.row] valueForKey:@"date"];

    cell.fecha_label.text = date;
    return cell;
}

I have tried other ways to check if the string is null, but I have been searching and this should be the way to check it.

Please tell me what is wrong in my code?

Upvotes: 0

Views: 87

Answers (3)

Hardik Kardani
Hardik Kardani

Reputation: 576

NSString *cabdriver = [[historialServicios objectAtIndex:indexPath.row] valueForKey:@"cabdriver"];

 if ((NSNull *)cabdriver != [NSNull null])
 {
      cell.conductor_label.text = cabdriver;
 }
else{
      cell.conductor_label.text = @"-";
}

Upvotes: 1

Vamshi Krishna
Vamshi Krishna

Reputation: 989

Try using this once:

if (![cabdriver isKindOfClass:[NSNull class]])
{
    cell.conductor_label.text = cabdriver;
}

Upvotes: 1

Steve
Steve

Reputation: 1840

When processing data returned from a server you should be prepared for any of the values to be null. I use the following two methods - one to check for a string, the other to check for a number:

- (NSString *)stringValueOfDictionaryObject:(id)dictionaryObject
{
    if (dictionaryObject == [NSNull null]) {
        return @"";
    }
    else {
        return (NSString *)dictionaryObject;
    }
}

- (NSNumber *)numericValueOfDictionaryObject:(id)dictionaryObject
{
    if (dictionaryObject == [NSNull null]) {
        return nil;
    }
    else {
        return (NSNumber *)dictionaryObject;
    }
}

In the case of your cab driver, you could do the following:

NSString *cabDriver = [self stringValueOfDictionaryObject:(id)[[historialServicios objectAtIndex:indexPath.row] valueForKey:@"cabdriver"]];

Note that if your cab driver value is null in your json file, the routine above will return an empty string (@""). You could change that to @"-" either in the routine or after getting your cabDriver NSString value.

Upvotes: 1

Related Questions