ios - 通过展开 segue 传递变量

Question

我有两个 Controller 通过展开的 segue 连接。第一个 View 有一个表，上面写着:Auction、Make、Model 作为三行。当用户点击“拍卖”行时，它会将他们发送到以前拍卖的表格 View 。

我想要做的是让拍卖(从第二个 View 中点击)显示在第一个 View 中。我有展开的 segue 工作，但是当我尝试创建一个静态变量来保存文本时，它在返回时将自身更改为 NULL 。例如，我设置了一个名为“label”的 static NSString。单击第二个 TableView 中的一行时，标签将更改为该单元格的文本值。但是当我将它传回 segue 时，它​​变为 NULL。

这是第一个 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

这是第二个 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

您的代码不起作用的原因是因为在 didSelectRowAtIndexPath 之前调用了 prepareForSegue。使用 segues 时，最好根本不实现 didSelectRowAtIndexPath。您可以获得从 prepareForSegue:sender: 中的 sender 参数中选择的单元格。您的代码应如下所示，

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

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

从单元格中获取数据通常也不是一个好的做法，单元格用于显示数据，而不是提供数据，但是您设置数据源的方式使这有点困难。与拥有多个数组不同，您可以通过拥有一个数组数组来获得更简洁的代码(这样您就不需要所有这些 else-if 了)。