Index through an array from within CellForRowAtIndexPath when there is no index

Question

I have populated a NSArray with results of a query from MagicalRecord (a Core Data wrapper). I need to take those results and display them in custom cells in a UITableView from within cellForRowAtIndexPath:, but the index refers to another UITableView that has been selected.

I have two UITableViews; one contains a list of customers, the other contains a list of appointments for each customer. When the user selects a customer, the code finds all of the appointments for that customer. As such, there is no index involved with the second table view).

The first table view has a list of clients; when the user selects one of those clients, the second table view is populated with a list of appointments for that selected client. Thus the index.row refers to the first UITableView and the second has no index it can refer to. I just dump the contents of the apptDataArrray into the cells.

Here is my code:

if(tableView.tag == 2) {  //  appointment info  
    static NSString *cellIdentifier = @"apptListCell";
    ApptCell *cell = [tableView dequeueReusableCellWithIdentifier:cellIdentifier];

    if(cell == nil)  {
        cell = [[ApptCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:cellIdentifier];
    }

    //  configure the cell...
    AppointmentInfo *currentAppointment = [apptDataArray objectAtIndex: 0];  //  go through the array  <---- TODO

    // Set the dateFormatter format
    NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
    NSDateFormatter *timeFormatter = [[NSDateFormatter alloc] init];
    [dateFormatter setDateFormat:@"yyyy-MM-dd HH:mm:ss"];  //  start date/time
    [timeFormatter setDateFormat:@"HH:mm:ss"];  //  end time

    UILabel *label = (UILabel *)[cell viewWithTag:3];  //  display start date/time  (NEEDS TO BE LOCALIZED!)<-----  TODO????
    label.text = [dateFormatter stringFromDate:currentAppointment.aStartTime];

    label = (UILabel *)[cell viewWithTag:4];  //  display end time
    label.text = [timeFormatter stringFromDate:currentAppointment.aEndTime];

    label = (UILabel *)[cell viewWithTag:5];  //  display service tech name
    label.text = currentAppointment.aServiceTech;

    return cell;

}

My question is: When at the line below // configure the cell, how do I iterate through the apptDataArray each time cellForRowAtIndexPath: is called, since there is NO index that can be applied to this array?

how does the array not have an index? Does it only contain a single object? If there is no index, what is the relationship between the array and cellForRowAtIndexPath? — propstm
– propstm, Commented Jan 7, 2013 at 16:45

jscs · Accepted Answer · 2013-01-07 19:16:43Z

from within cellForRowAtIndexPath: but the index refers to another UITableView that has been selected.

What?! No, it doesn't. You have a serious misunderstanding. The full name of that method is tableView:cellForRowAtIndexPath:. Any table view that needs to display a cell passes itself as the first argument, and it passes the index path for its own single cell* as the second. When the second table view is asking your data source for its cell information -- when your test tableView.tag == 2 test is true -- the passed-in index path refers to that table. How could it possibly work otherwise?

All you need to do is

AppointmentInfo *currentAppointment = [apptDataArray objectAtIndex: indexPath.row];

the same as you would for any other array-backed table view.

There's no magic going on here. You've given the table view a pointer to your object and told the table to get information it needs from that object. The table then sends messages, just like anything else, to the data source object. One of those messages is tableView:cellForRowAtIndexPath:. The fact that another table view also sends that message sometimes doesn't affect the first. Each table view will interact with your data source only on its own behalf.

As a note, this problem -- even the description of your app's structure -- indicates strongly that you should probably have a separate data source/delegate object for each of your table views.

*Somewhere in the comments you seemed to imply that you think you need to set up all the cells in the table view during one call of tableView:cellForRowAtIndexPath:, and that's not right either. You need to configure and return just the one single cell that corresponds to the index path.

Damn! Indeed it does! Thank you, Josh, for the clarification. And for what it's worth - I at least got the part right about returning ONE cell... learned something new today... thanks again!

propstm · Accepted Answer · 2013-01-07 18:48:39Z

1

It sounds like you need to create an array of appointments for each client, then assuming that array is called apptDataArray the below code will work. Clicking an row on the first tableview will use the client to create an appointment array list and reload the second tableview with that data. Each appointment is a row.

If you are getting all your data and all of your results are stored in apptDataArray then you should be able to set your tableviewNumberOfRows value to size of the apptDataArray

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section{
    if(tableView == table2Ivar){
      return [apptDataArray count];
    }
   //Else you are getting a list of unique clients
}

Then using the correlation between result entries and table rows when you configure your cell just use and each indexpath.row will be an entry for a client appointment.

AppointmentInfo *currentAppointment = [apptDataArray objectAtIndex: indexPath.row];

Sample GitHub Project https://github.com/propstm/twoTableTest

edited Jan 7, 2013 at 18:48

answered Jan 7, 2013 at 16:52

propstm

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5 Comments

SpokaneDude Over a year ago

No, that won't work... see UPDATE above... there are multiple appointments per client. I was thinking of using a singleton as the index to the apptDataArray from within cellForRowAtIndexPath.

SpokaneDude Over a year ago

That won't work either... I already set numberOfRowsInSection based on which UITableView is accessed. The problem is there is no way (other than using a singleton) to iterate through the apptDataArray from WITHIN the cellForRowAtIndexPath. If you have 4 rows in apptDataArray, each time you go through CellForRowAtIndexPath, any integer you use for an index will be reset (ie in a Foreach statement), unless it's a singleton. I was hoping there would be another way of doing it other than singleton.

propstm Over a year ago

Does the client object that you are using for tableview1 have any sort of grouping for client appointments on a client level? I'm wondering if you could do something like getting the object from the selected row in table one, and accessing the data from there to populate 2nd tableview?

SpokaneDude Over a year ago

That's exactly what I do... select client in table-1, create the key from name and last-4 of phone number, and access all of the records in the Core Data store using that key. MagicalRecord returns the result in a NSArray, which then has to be populated to the cells in table-2.

propstm Over a year ago

I just created a chat room chat.stackoverflow.com/rooms/22335/…

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