UITableView：NSMutableArray没有出现在表中

Question

I'm new to objective c and iPhone programming. I can't seem to figure out why no cells will fill when I run this code. The xml content displays in the console log and xcode displays no errors. Can any help?

    - (void)parser:(NSXMLParser *)parser didStartElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName attributes:(NSDictionary *)attributeDict
{
    if(![elementName compare:@"Goal"]) {
        tempElement = [[xmlGoal alloc] init];
    } else if (![elementName compare:@"Title"]) {
        currentAttribute = [NSMutableString string];
    } else if (![elementName compare:@"Progress"]) {
        currentAttribute = [NSMutableString string];
    }
}

- (void)parser:(NSXMLParser *)parser didEndElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName
{
    if (![elementName compare:@"Goal"])  {
        [xmlElementObjects addObject:tempElement];
    } else if (![elementName compare:@"Title"]) {
        NSLog(@"The Title of this event is %@", currentAttribute);
        [tempElement setTitled:currentAttribute];
     } else if (![elementName compare:@"Progress"]) {
        NSLog(@"The Progress of this event is %@", currentAttribute);
        [tempElement setProgressed:currentAttribute];
    }
}

- (void)parser:(NSXMLParser *)parser foundCharacters:(NSString *)string
{
    if (self.currentAttribute) {
        [self.currentAttribute appendString:string];
    }
}

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
    return [xmlElementObjects count];
}

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
    static NSString *CellIdentifier = @"Cell";
    UITableViewCell *cell = [mtableview dequeueReusableCellWithIdentifier:CellIdentifier];
    if (cell == nil) {
        cell = [[[UITableViewCell alloc] initWithFrame:CGRectZero reuseIdentifier:CellIdentifier] autorelease];
    }
    // Set up the cell...
    cell.textLabel.text = [xmlElementObjects objectAtIndex:indexPath.row];
    return cell;
}

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath {   

}

Answer 1

I can't seem to figure out why no cells will fill when I run this code.

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
    return [xmlElementObjects count];
}

Is this method getting hit? If so, is xmlElementObjects nil ? If not, is it returning 0 since there are no elements in the array? If so, is it because your XML parsing code didn't fill the array before the array is being used?

Answer 2

Another thing you need to check: Did you set the dataSource property of your tableview to the correct object? Other than that, check if your if(![elementName compare:@"Goal"]) is really 'hit' (either by NSLog()ing or putting a breakpoint there.

Another note, and unrelated, you should probably release tempElement after adding it to the xmlElements dictionary.

Answer 3

Set breakpoints in -tableView:numberOfRowsInSection: and -tableView:cellForRowAtIndexPath: to ensure that they're being called. As Alfons mentioned, it may be that your table view's datasource property is not being set.

Some unrelated notes:

1. Why are you using the statement ![someString compare:someOtherString] for comparison? NSString has a built-in -isEqualToString: method, so you can replace that statement with [someString isEqaulToString:someOtherString] . Your results won't change, but your code will benefit from the added readability.

2. In -tableView:cellForRowAtIndexPath: , you have the following code:

    UITableViewCell *cell = [mtableview dequeueReusableCellWithIdentifier:CellIdentifier]; 

   This might cause problems if you keep using the instance variable (in this case, mtableview ) here. The method has a table view as an argument, so use tableView instead. That will ensure that you dequeue a cell from the table view that called this method.

3. Are you developing for iPhone OS 3.0 or above? If so, the line

    [[UITableViewCell alloc] initWithFrame:CGRectZero reuseIdentifier:CellIdentifier]; 

   should be replaced with

    [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier]; 

   using whichever cell style you'd like, naturally.

Answer 4

Well xmlElementObjects isn't a array of strings, it contains instances to some custom class you've created (I assume). Thus, when you say cell.textLabel.text = [xmlElementObjects objectAtIndex:indexPath.row]; , you're setting a NSString to some unknown object.

Try cell.textLabel.text = [[xmlElementObjects objectAtIndex:indexPath.row] titled];

(I'm guessing the title name from the parsing code)

Answer 5

Objective C is very new to me. I am used to writing PHP which seems very easy compared to this so far. I set the datasource and also change compare to isequaltostring. This is what the console log states now:

2010-04-07 02:28:16.580 bucket list[6449:20b] The Title of this event is Test 1 10%

2010-04-07 02:28:16.581 bucket list[6449:20b] The Title of this event is Test 2 20%

2010-04-07 02:28:16.584 list[6449:20b] * -[xmlGoal isEqualToString:]: unrecognized selector sent to instance 0x3d36600 2010-04-07 02:28:16.585 list[6449:20b] * Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '*** -[xmlGoal isEqualToString:]: unrecognized selector sent to instance 0x3d36600'

I appreciate all the help!