Can't Get indexPath.row from a array (error indexPath undeclared)?

I declared a NSArray in my .h

@interface DevicePreferencesController : UITableViewController < UIAlertViewDelegate >{
    NSArray *plist;
    UITextField *deviceName;
}

This array is use to load a plist data from URL

and this is the plist I got

plist:(
        {
        category = 11;
        id = 1;
        name = light1;
    },
        {
        category = 11;
        id = 5;
        name = window;
    },
        {
        category = 12;
        id = 2;
        name = dimmer2;
    },
        {
        category = 23;
        id = 3;
        name = win;
    }
)

I show It by a tableView

and if I selected the cell

It will pop up an alertView with a textField,it can rename the data in the plist

And here is the button action for alertView

- (void)alertView:(UIAlertView *)alertView clickedButtonAtIndex:(NSInteger)buttonIndex {
if ([alertView tag]==1) {
        if (buttonIndex == 1){
            [request setPostValue:[[self.plist objectAtIndex:indexPath.row] valueForKey:@"id"]  forKey:@开发者_JAVA技巧"id"];
            [request setPostValue:deviceName.text  forKey:@"name"];
            [request startSynchronous];
        }
    }
}

But I got error here "indexPath" undeclared !

Why ? plist is an array ,why can't I get indexPath from an array ???

'indexPath' is not your variable, so that is because it's undeclared. You should store the indexPath in the tableview didselectedrow method, to a local variable, and use it in the alertView delegate method.

indexPath is available as part of TableView's Delegate and DataSource methods. Do you have a variable named indexPath as a global variable or as a memeber variable in your class?