objective-c - 如何将 NSMutableArray 传递给另一个 ViewController 类

Question

我在 "HeroListViewController" 中创建了 NSMutale 数组。我想在另一个 viewController 中使用它，它是 MapTutorialViewController。我试过这样。

在 HeroListViewController.h 中

MapTutorialViewController *maptutorialcontroller;
NSMutableArray *listData; 

设置属性并正确合成它们

在 HeroListViewController.m 中

- (void)viewDidLoad {
    [super viewDidLoad];

    listData = [[NSMutableArray alloc] init];   
    }

 - (UITableViewCell *)tableView:(UITableView *)theTableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {

static NSString *HeroTableViewCell = @"HeroTableViewCell";

UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:HeroTableViewCell];
if (cell == nil) {
    cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:HeroTableViewCell] autorelease];
}
NSManagedObject *oneHero = [self.fetchedResultsController objectAtIndexPath:indexPath];
NSInteger tab = [tabBar.items indexOfObject:tabBar.selectedItem];
switch (tab) {
    case kByName:
        cell.textLabel.text = [oneHero valueForKey:@"name"];
        cell.detailTextLabel.text = [oneHero valueForKey:@"secretIdentity"];
        break;
    case kBySecretIdentity:
        cell.detailTextLabel.text = [oneHero valueForKey:@"name"];
        cell.textLabel.text = [oneHero valueForKey:@"secretIdentity"];
    default:
        break;
}

        [listData addObject: [oneHero valueForKey:@"secretIdentity"]];


        count=[listData count];
                printf("No of items of listData:%u\n", count);


if(maptutorialcontroller==nil){
      maptutorialcontroller= [[MapTutorialViewController    alloc]initWithNibName:@"MapTutorialViewController" bundle:nil];
maptutorialcontroller.secondarray=listData;
}
count=[maptutorialcontroller.secondarray count];
printf("No of items of seconarray :%u\n", count);

return cell;

输出: listData 的项目数:3 seconarray 的项数 :3//都正确

但是我遇到的问题是，当我尝试像这样在“MapTutorialViewController”中使用辅助数组时，在 MapTutorialViewController.h 中

    HeroListViewController *heroviewcontroller;
  NSMutableArray *secondarray; 

设置属性并正确合成它们

在 MapTutorialViewController.m 中

 - (void)viewDidLoad 
   {
    heroviewcontroller = [[HeroListViewController alloc]initWithNibName:@"HeroListViewController"  bundle:nil]; 
   self.secondarray=[heroviewcontroller.listData mutableCopy];
   //secondarray= heroviewcontroller.listData;
int count;
count = [secondarray count];
//  
   printf("No of items of secondarray from MapTutorialViewContriller :%u\n", count);
   }

输出:来自 MapTutorialViewContriller 的 secondarray 的项目数:0
为什么是0

我的代码有什么问题，请帮助我

Answer 1

示例

firstviewcontroller .h file

        before @interface 

        use @class secondViewcontroller;


declare this inside of @interface  with

        secondViewcontroller *sVC;


then in firstViewController.m file 

        before @implementation          

    #import "secondViewcontroller.h"

then
-------------------

secondVC.h file

        @interface inside declare this

        say NSMutableArray *secondarray;

        and sythasize them.

------------------- 

after this 

        in firstViewcontroller.h viewdidload create this sVC by alloc and initwithnibname then

        sVC.secondArray=urfirstArray;

        now while u push this sVC controller to navigation controller u can nslog this array in viewdidload.