UITableView multiselect - objective-c

Question

I have a uitableview with 50 rows populated from a predefined nsarray.
How can I select multiple the rows with say maximum 3 allowed at a time and show check when selected and remove check when deselected/
I am really new to xcode and any help is much appreciated. Thank you.

Answer 1

Your data needs to keep track of whether it is selected or not.
Two common ways are: each object in your predefined array has a BOOL that indicates whether or not it is selected, or you keep a second array that holds only references to selected objects. Since you're limited to three selected, the second option might be better.
When someone selects a cell in your table, you change the selection status of the related object, either switching its BOOL or adding/removing it in the extra array. This is also the place to check whether you already have as many selections as you allow. If selections have changed, you then tell your table to reload data.
In cellForRowAtIndexPath: you check whether or not the object is selected and mark it accordingly.

Answer 2

int counter = 0; //keep track of how many rows are selected
int maxNum = 3; //Most cells allowed to be selected
//Called when the user selects a row
- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
UITableViewCell *cell = [tableView cellForRowAtIndexPath:indexPath];
//If the cell isn't checked and there aren't the maximum allowed selected yet
if (cell.accessoryType != UITableViewCellAccessoryCheckmark && counter < maxNum)
{
cell.accessoryType = UITableViewCellAccessoryCheckmark;
counter++;
}
else if (counter >= maxNum) return; //Don't do anything if the cell isn't checked and the maximum has been reached
else //If cell is checked and gets selected again, deselect it
{
cell.accessoryType = UITableViewCellAccessoryNone;
counter--;
}
}
You might also want to keep an array of indices of the cells that are selected, in case you want to do something with the data that's in them. If you don't know how to do this, let me know and I'll add the code.
Notes:
You need to be implementing the table view delegate protocol in order to have this method called correctly.
This isn't the "best" way to do it (using cell content to keep track of selection is generally frowned up) but it is very easy.
You might run into problems with cell reuse. If you want to fix that, store the cell's index and set the accessory type in cellForRowAtIndexPath