Passing variable through unwinding segue

Question

I have two controllers connected through an unwinding segue. The first view has a table that says: Auction, Make, Model as the three rows. When the user clicks the "Auction" row, it sends them to a tableview of previous auctions.

What I want to do is have the auction (clicked on from the second view) show up on the first view. I have the unwinding segue working, but when I tried creating a static variable to hold the text, it changes itself to NULL when segueing back. For example, I have set a static NSString called 'label'. When a row in the second tableview is clicked, label is changed to that cell's text value. But when I pass it back in the segue, it changes to NULL .

Here is the first view:

#import "searchCar.h"
#import "auctionTable.h"
@implementation searchCar
@synthesize auctionLabel;

- (IBAction)unwindToList:(UIStoryboardSegue *)segue
{
    auctionTable *unwoundSegue = segue.sourceViewController;
    self.auctionLabel.text = unwoundSegue.auctionName;
}

@end

Here is the second view:

#import "searchCar.h"
#import "auctionTable.h"

static NSString *label;

@implementation auctionTable
@synthesize auctionName;

- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.

    //Default section data
    self.defaultItemsArray=@[@"All"];

    //First section data
    self.firstItemsArray = @[@"Houston, TX 4/2014",@"Davenport, IA 4/2014",@"Kissimmee, FL 1/2014",@"Las Vegas, NV 1/2014"];

//Second section data
self.secondItemsArray = @[@"Kansas City, MO 12/2013",
                             @"Anaheim, CA 11/2013",
                             @"Davenport, IA 11/2013",
                             @"Schaumburg, IL 10/2013",
                             @"Dallas, TX 9/2013",
                             @"Monterey, CA 8/2013",
                             @"Walworth, WI 8/2013",
                             @"Santa Monica, CA 7/2013",
                             @"Des Moines, IA 7/2013",
                             @"West Allis, WI 7/2013",
                             @"Champaign , IL 6/2013",
                             @"Indianapolis, IN 5/2013",
                             @"Kansas City, MO 4/2013",
                             @"Houston, TX 4/2013",
                             @"Davenport, IA 4/2013",
                             @"Boynton Beach, FL 2/2013",
                             @"Kissimmee, FL 1/2013"];

//Third section data
self.thirdItemsArray = @[@"Kansas City, MO 12/2012",
                            @"Anaheim, CA 11/2012",
                            @"Davenport, IA 11/2012",
                            @"St Charles, IL 10/2012",
                            @"Dallas, TX 9/2012",
                            @"Monterey, CA 8/2012",
                            @"Walworth, WI 8/2012",
                            @"Des Moines, IA 7/2012",
                            @"West Allis, WI 7/2012",
                            @"St. Charles, IL 6/2012",
                            @"St. Paul, MN 6/2012",
                            @"North Little Rock, AR 6/2012",
                            @"Indianapolis, IN 5/2012",
                            @"Houston, TX 4/2012",
                            @"Walworth, WI 4/2012",
                            @"Kansas City, MO 3/2012",
                            @"Kissimmee, FL 1/2012"];

//Fourth section data
self.fourthItemsArray = @[@"Kansas City, MO 12/2011",
                             @"Dallas, TX 10/2011",
                             @"Fontana, WI 9/2011",
                             @"St. Charles, IL 9/2011",
                             @"Monterey, CA 8/2011",
                             @"Walworth, WI 8/2011",
                             @"Des Moines, IA 7/2011",
                             @"West Allis, WI 7/2011",
                             @"St. Charles, IL 6/2011",
                             @"St. Paul, MN 6/2011",
                             @"Indianapolis, IN 5/2011",
                             @"Walworth, WI 3/2011",
                             @"Kansas City, MO 3/2011",
                             @"Kissimmee, FL 1/2011"];

//Fifth section data
self.fifthItemsArray = @[@"Kansas City, MO 12/2010",
                            @"Canal Winchester, OH 11/2010",
                            @"Ft. Lauderdale, FL 10/2010",
                            @"Winsted, MN 10/2010",
                            @"St. Charles, IL 9/2010",
                            @"Monterey, CA 8/2010",
                            @"Walworth, WI 8/2010",
                            @"Des Moines, IA 7/2010",
                            @"St. Charles, IL 6/2010",
                            @"St. Paul, MN 6/2010",
                            @"Indianapolis, IN 5/2010",
                            @"Kansas City, MO 4/2010",
                            @"Kissimmee, FL 1/2010"];

//Sixth section data
self.sixthItemsArray = @[@"Kansas City, MO 12/2009",
                            @"Branson, MO 10/2009",
                            @"St. Charles, IL 10/2009",
                            @"Canal Winchester, OH 9/2009",
                            @"Monterey, CA 8/2009",
                            @"Des Moines, IA 7/2009",
                            @"St. Charles, IL 6/2009",
                            @"St. Paul, MN 6/2009",
                            @"Indianapolis, IN 5/2009",
                            @"Kansas City, MO 3/2009",
                            @"Kissimmee, FL 1/2009"];

//Seventh section data
self.seventhItemsArray = @[@"Kansas City, MO 12/2008",
                              @"St. Charles, IL 10/2008",
                              @"Canal Winchester, OH 9/2008",
                              @"Des Moines, IA 7/2008",
                              @"St. Charles, IL 6/2008",
                              @"St. Paul, MN 6/2008",
                              @"Indianapolis, IN 5/2008",
                              @"Kissimmee, FL 1/2008"];

}


 - (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView {
return 7;
}


- (NSString *)tableView:(UITableView *)tableView titleForHeaderInSection:(NSInteger)section {

if(section == 0)
    return @"Default";
else if(section == 1)
    return @"2014";
else if(section == 2)
    return @"2013";
else if(section == 3)
    return @"2012";
else if(section == 4)
    return @"2011";
else if(section == 5)
    return @"2010";
else if(section == 6)
    return @"2009";
else if(section == 7)
    return @"2008";
else
    return 0;
}

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:  (NSInteger)section
{
if(section == 0)
    return [self.defaultItemsArray count];
else if(section == 1)
    return [self.firstItemsArray count];
else if(section == 2)
    return [self.secondItemsArray count];
else if(section == 3)
    return [self.thirdItemsArray count];
else if(section == 4)
    return [self.fourthItemsArray count];
else if(section == 5)
    return [self.fifthItemsArray count];
else if(section == 6)
    return [self.sixthItemsArray count];
else if(section == 7)
    return [self.seventhItemsArray count];
else
    return 0;
}

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:    (NSIndexPath *)indexPath
{
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:@"auctionCell"];

if(indexPath.section == 0)
{
    cell.textLabel.text = [self.defaultItemsArray    objectAtIndex:indexPath.row];
}
else if(indexPath.section == 1)
{
    cell.textLabel.text = [self.firstItemsArray    objectAtIndex:indexPath.row];
}
else if(indexPath.section == 2)
{
    cell.textLabel.text = [self.secondItemsArray    objectAtIndex:indexPath.row];
}
else if(indexPath.section == 3)
{
    cell.textLabel.text = [self.thirdItemsArray    objectAtIndex:indexPath.row];
}
else if(indexPath.section == 4)
{
    cell.textLabel.text = [self.fourthItemsArray    objectAtIndex:indexPath.row];
}
else if(indexPath.section == 5)
{
    cell.textLabel.text = [self.fifthItemsArray    objectAtIndex:indexPath.row];
}
else if(indexPath.section == 6)
{
    cell.textLabel.text = [self.sixthItemsArray    objectAtIndex:indexPath.row];
}
else if(indexPath.section == 7)
{
    cell.textLabel.text = [self.seventhItemsArray    objectAtIndex:indexPath.row];
}
else{
    cell.textLabel.text = @"Not Found";
}

return cell;
}



- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath {
UITableViewCell *cell = [tableView cellForRowAtIndexPath:indexPath];

label = cell.textLabel.text;
}

-(void) prepareForSegue: (UIStoryboardSegue *)segue sender: (id)sender {
if ([segue.identifier isEqualToString:@"completeEntry"]) {
    self.auctionName = label;
}
}

@end

Answer 1

The reason your code doesn't work is because prepareForSegue is called before didSelectRowAtIndexPath. When using segues, it's better to not implement didSelectRowAtIndexPath at all. You can get the cell that was selected from the sender argument in prepareForSegue:sender:. Your code should look like this,

-(void) prepareForSegue: (UIStoryboardSegue *)segue sender: (UITableViewCell *)sender {

    if ([segue.identifier isEqualToString:@"completeEntry"]) {
        _label = sender.textLabel.text;
        self.auctionName = _label;
    }
}

It's also not usually a good practice to get data from a cell, cells are for displaying data, not providing it, but the way you set up your data source makes that a little difficult. Instead of having multiple arrays, you would have far cleaner code by having a single array of arrays (then you wouldn't need all those else-if's).

Answer 2

Why don't you just use

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

   UITableViewCell *cell = [tableView cellForRowAtIndexPath:indexPath];
   self.auctionName = cell.textLabel.text;
}

? and get rid of the prepareForSegue in auctionTable

You don't show the @property definition for auctionName but it should be defined as

@property (copy,nonatomic) NSString *auctionName

The copy will ensure you get a copy of a string rather than reference to a string that may be deallocated.

By, the way, as a matter of style, auctionTable should be AuctionTable and searchCar should be SearchCar - classes start with a capital letter.