tableview crash with '*** -[__NSArrayM insertObject:atIndex:]: object cannot be nil' - ios

Question

I got a problem.
I have a TableView in my ViewController. This TableView has 5 rows with textFields. The height of each row is 156 pixels. also I have button "Save", and after click I want save all my data to NSMutableArray in following method, but in result I got an error.
What should I do in this way?
thank you
my method example:
- (void) saveDataToArray
{
carCellTableViewCell * cell;
_carNewPrices = [[NSMutableArray alloc] init];
for (int i = 0; i < 5; i++)
{
cell = (carCellTableViewCell *)[_meTableView cellForRowAtIndexPath:[NSIndexPath indexPathForRow:i inSection:0]];
[_carPrices addObject:cell.priceText.text];
}
}
and here is cellForRowAtIndexPath:
- (UITableViewCell *) tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
carCellTableViewCell * cell = [tableView dequeueReusableCellWithIdentifier:#"cell"];
cell.nameLabel.text = [_carNames objectAtIndex:indexPath.row];
cell.priceLabel.text = [NSString stringWithFormat:#"$%#/day",[_carPrices objectAtIndex:indexPath.row]];
cell.infoLabl.text = [_carInfos objectAtIndex:indexPath.row];
switch (indexPath.row) {
case 0:
{
[cell.img setImage:[UIImage imageNamed:#"rolls.jpg"]];
return cell;
}
case 1:
{
[cell.img setImage:[UIImage imageNamed:#"bentley.jpg"]];
return cell;
}
case 2:
{
[cell.img setImage:[UIImage imageNamed:#"mercedes.jpg"]];
return cell;
}
case 3:
{
[cell.img setImage:[UIImage imageNamed:#"bmw.jpg"]];
return cell;
}
case 4:
{
[cell.img setImage:[UIImage imageNamed:#"skoda.jpg"]];
}
default:
break;
}
return cell;
}
additional:
in my tableviewCell i have a label, and a textfield. when i click on "Save" i want save all my data from textField and send it to label.
here is all code from .m file:
#import "carListViewController.h"
#import "carCellTableViewCell.h"
#import "UserSingleton.h"
#import "CheckInternetConnection.h"
#define getCarList #"http:mylink.php" //changed
#define setCarList #"http:mylink.php" //changed
#interface carListViewController ()
#property (weak, nonatomic) IBOutlet UIBarButtonItem *editButtonOutler;
- (IBAction)editButtonOnClick:(id)sender;
#property BOOL editOrSave;//0 when edit, 1 when save
#property UserSingleton * userInfo;
#property NSMutableArray *json;
#property NSMutableArray * carNames;
#property NSMutableArray * carPrices;
#property NSMutableArray * carInfos;
#property NSMutableArray * carNewPrices;
- (void) setData;
#property (weak, nonatomic) IBOutlet UITableView *meTableView;
- (void) saveDataToArray;
- (void) getDataOfCars;
#end
#implementation carListViewController
- (void)viewDidLoad
{
[super viewDidLoad];
self.title = #"List of cars";
// Do any additional setup after loading the view.
}
- (void) viewWillAppear:(BOOL)animated
{
CheckInternetConnection * checkInternet = [[CheckInternetConnection alloc] init];
if (![checkInternet isInternetAvailable])
[self.navigationController popViewControllerAnimated:YES];
_userInfo = [UserSingleton sharedInstance];
if (_userInfo.priority == 2)
{
_editButtonOutler.enabled = YES;
_editButtonOutler.title = #"Edit";
}
else
{
_editButtonOutler.enabled = NO;
_editButtonOutler.title = #"";
}
_editOrSave = NO;
[self getDataOfCars];
[_meTableView reloadData];
}
- (NSInteger) numberOfSectionsInTableView:(UITableView *)tableView
{
return 1;
}
- (NSInteger) tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
return 5;
}
- (UITableViewCell *) tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
carCellTableViewCell * cell = [tableView dequeueReusableCellWithIdentifier:#"cell"];
cell.nameLabel.text = [_carNames objectAtIndex:indexPath.row];
cell.priceLabel.text = [NSString stringWithFormat:#"$%#/day",[_carPrices objectAtIndex:indexPath.row]];
cell.infoLabl.text = [_carInfos objectAtIndex:indexPath.row];
switch (indexPath.row) {
case 0:
{
[cell.img setImage:[UIImage imageNamed:#"rolls.jpg"]];
return cell;
}
case 1:
{
[cell.img setImage:[UIImage imageNamed:#"bentley.jpg"]];
return cell;
}
case 2:
{
[cell.img setImage:[UIImage imageNamed:#"mercedes.jpg"]];
return cell;
}
case 3:
{
[cell.img setImage:[UIImage imageNamed:#"bmw.jpg"]];
return cell;
}
case 4:
{
[cell.img setImage:[UIImage imageNamed:#"skoda.jpg"]];
}
default:
break;
}
return cell;
}
- (IBAction)editButtonOnClick:(id)sender {
if (_editOrSave == 0)
{
_editOrSave = 1;
_editButtonOutler.title = #"Save";
carCellTableViewCell * cell;
for (int i = 0; i < 5; i ++)
{
cell = (carCellTableViewCell *)[_meTableView cellForRowAtIndexPath:[NSIndexPath indexPathForRow:i inSection:0]];
cell.priceLabel.hidden = YES;
cell.priceText.hidden = NO;
cell.priceText.text = [[_json objectAtIndex:i] objectForKey:#"cost"];
}
}
else if (_editOrSave == 1)
{
_editOrSave = 0;
carCellTableViewCell * cell;
for (int i = 0; i < 5; i ++)
{
cell = (carCellTableViewCell *)[_meTableView cellForRowAtIndexPath:[NSIndexPath indexPathForRow:i inSection:0]];
cell.priceLabel.hidden = NO;
cell.priceText.hidden = YES;
[self saveDataToArray];
[self setData];
//cell.priceLabel.text = [_carPrices objectAtIndex:i];
}
_editButtonOutler.title = #"Edit";
}
[self getDataOfCars];
[_meTableView reloadData];
}
- (void) getDataOfCars
{
_carInfos = [[NSMutableArray alloc] init];
_carNames = [[NSMutableArray alloc] init];
_carPrices = [[NSMutableArray alloc] init];
NSURLRequest* urlRequest = [NSURLRequest requestWithURL:[NSURL URLWithString:getCarList] cachePolicy:NSURLRequestUseProtocolCachePolicy timeoutInterval:60.0];
NSData * data = [NSURLConnection sendSynchronousRequest:urlRequest returningResponse:nil error:nil];
_json = [NSJSONSerialization JSONObjectWithData:data options:kNilOptions error:nil];
carCellTableViewCell * cell;
for (int i = 0; i < _json.count; i ++)
{
cell = (carCellTableViewCell *)[_meTableView cellForRowAtIndexPath:[NSIndexPath indexPathForRow:i inSection:0]];
[_carNames addObject:[[_json objectAtIndex:i] objectForKey:#"name"]];
[_carPrices addObject:[[_json objectAtIndex:i] objectForKey:#"cost"]];
[_carInfos addObject:[[_json objectAtIndex:i] objectForKey:#"about"]];
}
}
- (void) setData{
for (int i = 0; i < 5; i ++)
{
NSMutableString * postString = [NSMutableString stringWithFormat:setCarList];
[postString appendString:[NSString stringWithFormat:#"?id=%d", i+1]];
[postString appendString:[NSString stringWithFormat:#"&cost=%#", [_carPrices objectAtIndex:i]]];
[postString setString:[postString stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding]];
NSMutableURLRequest * request = [[NSMutableURLRequest alloc] initWithURL:[NSURL URLWithString:postString]];
[request setHTTPMethod:#"POST"];
NSURLConnection * postConnection;
postConnection = [[NSURLConnection alloc] initWithRequest:request delegate:self startImmediately:YES];
}
}
- (void) saveDataToArray
{
carCellTableViewCell * cell;
_carNewPrices = [[NSMutableArray alloc] init];
for (int i = 0; i < 5; i++)
{
cell = (carCellTableViewCell *)[_meTableView cellForRowAtIndexPath:[NSIndexPath indexPathForRow:i inSection:0]];
[_carPrices addObject:cell.priceText.text];
}
}
#end
it seems that an error is caused because not all cells are visible in the screen. after my scroll down now even last cell has changed after my onclick on edit button.
how to resovle this problem?

Answer 1

It's upside-down to fill an array with what's in a UITableView. The way to do that is the other way around.
In other words, somewhere else in your code you determine what's in the priceText label. If it's a static table, then the information might be in IB, or if you're implementing tableview:cellForRowAtIndexPath:, you're looking up the priceText there.
Put those values in the priceArray.
Your edit helped. This line:
[NSString stringWithFormat:#"$%#/day",[_carPrices objectAtIndex:indexPath.row]];
Is your friend, so:
NSMutableArray *newArrayOfStrings = [NSMutableArray array];
for (int i=0; i<_carPrices.count; i++) {
NSString *str = [NSString stringWithFormat:#"$%#/day",_carPrices[i]];
[newArrayOfStrings addObject:str];
}
Edit again. More code and comments, more clarity:
Declare that your vc implements the UITextFieldDelegate, and declare a property to keep your edited prices:
#interface MyViewController <UITextFieldDelegate>
#property (nonatomic, strong) NSMutableArray *editedStrings;
// initialize this with the carPrices after you get these from JSON
self.editedStrings = [_carPrices mutableCopy]; // if they are NSNumbers
// if they are strings, you'll need a deeper copy:
self.editedStrings = [NSMutableArray array];
for (NSString *str in _carPrices) {
[self.editedStrings addObject:[str copy]];
}
In cellForRowAtIndexPath, make your vc the delegate, and tag the textFields, so you know which one is being edited:
cell.priceLabel.delegate = self;
cell.priceLabel.tag = indexPath.row;
Then implement the delegate method for when the user edits:
- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string {
NSInteger index = textField.tag;
NSString *candidateString = [textField.text stringByReplacingCharactersInRange:range withString:string];
[self.editedStrings replaceObjectAtIndex:index withObject: candidateString];
return YES;
}

Answer 2

Add a breakpoint to the line [_carPrices addObject:cell.priceText.text] and you'll see that at some index, the text will be nil. I can't tell you why will it be nil, since I don't know how you're creating the cell.