消失的 NSMutableArray，导致 UiTableView 显示空白单元格答案

【问题标题】：Disappearing NSMutableArray, causes UiTableView to show blank cells消失的 NSMutableArray，导致 UiTableView 显示空白单元格
【发布时间】：2011-11-03 16:09:30
【问题描述】：

我有一个显示食谱列表的 UITableView。我使用自定义类Recipe 创建每个食谱，然后将这些食谱放入一个msmutable 数组“recipes”中。问题是，当我开始滚动“食谱”数组时，它似乎丢失了所有数据（计数为 0）。这意味着进入视野的单元格不能显示任何配方信息。到底发生了什么？为什么数组消失了？

代码如下：

// .h

#import "CustomCell.h"
#import "Recipe.h"
@interface ViewController : UIViewController <UITableViewDataSource, UITableViewDelegate>
@property (weak, nonatomic) IBOutlet UITableView *recipeTableView;
@property (weak, nonatomic) NSMutableArray *recipes;


// .m
@synthesize recipeTableView;
@synthesize Recipes;

- (void)viewDidLoad
{
    [super viewDidLoad];
   Recipe *recipe1 = [[Recipe alloc] initWithCategory:@"Seafood" title:@"Recipe 1"];
    recipe1.recipeImage = [UIImage imageNamed:@"recipeImage1.png"];

    Recipe *recipe2 = [[Recipe alloc] initWithCategory:@"Seafood" title:@"Recipe 2"];
    recipe2.recipeImage = [UIImage imageNamed:@"recipeImage2.png"];

    Recipe *recipe3 = [[Recipe alloc] initWithCategory:@"Seafood" title:@"Recipe 3"];
    recipe3.recipeImage = [UIImage imageNamed:@"recipeImage3.png"];

    Recipe *recipe4 = [[Recipe alloc] initWithCategory:@"Seafood" title:@"Recipe 4"];
    recipe4.recipeImage = [UIImage imageNamed:@"recipeImage4.png"];

    Recipe *recipe5 = [[Recipe alloc] initWithCategory:@"Seafood" title:@"Recipe 5"];
    recipe5.recipeImage = [UIImage imageNamed:@"recipeImage5.png"];

    Recipe *recipe6 = [[Recipe alloc] initWithCategory:@"Seafood" title:@"Recipe 6"];
    recipe6.recipeImage = [UIImage imageNamed:@"recipeImage6.png"];

    Recipe *recipe7 = [[Recipe alloc] initWithCategory:@"Seafood" title:@"Recipe 7"];
    recipe7.recipeImage = [UIImage imageNamed:@"recipeImage7.png"];

    Recipe *recipe8 = [[Recipe alloc] initWithCategory:@"Seafood" title:@"Recipe 8"];
    recipe8.recipeImage = [UIImage imageNamed:@"recipeImage8.png"];

    Recipe *recipe9 = [[Recipe alloc] initWithCategory:@"Seafood" title:@"Recipe 9"];
    recipe9.recipeImage = [UIImage imageNamed:@"recipeImage9.png"];

    Recipe *recipe10 = [[Recipe alloc] initWithCategory:@"Seafood" title:@"Recipe 10"];
    recipe10.recipeImage = [UIImage imageNamed:@"recipeImage10.png"];


    recipes = [NSMutableArray arrayWithObjects:recipe1, recipe2, recipe3, recipe4, recipe5, recipe6, recipe7, recipe8, recipe9, recipe10, nil];

}




- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    Recipe *recipe = (Recipe*)[recipes objectAtIndex:indexPath.row];
    static NSString *CellIdentifier = @"RecipeCell";
    CustomCell *cell = (CustomCell *) [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
    cell.selectionStyle = UITableViewCellSelectionStyleNone;
    cell.titleLabel.text = recipe.title;
    return cell;
}

【问题讨论】：

像这样声明属性：@property (strong, nonatomic) NSMutableArray *shows;

标签： objective-c ios uitableview nsmutablearray automatic-ref-counting

【解决方案1】：

您的数组正在自动释放，请在配方分配后添加以下内容...

[recipes retain];

或者将创建数组的方式更改为...

recipes = [[NSMutableArray alloc] initWithObjects:.... etc

如果您在 iOS5 中使用 ARC，那么您应该将您的 recipes 变量声明为 strong，这可以有效地为您保留。

【讨论】：

谢谢，改用强工作。我对 ARC 的第一次尝试令人困惑。

【解决方案2】：

@simon 是对的。此外，recipeTableView 应该是 (nonatomic, strong)，因为您希望在加载视图时保留它。一般来说，除非/直到你有特定的理由需要一个，否则我会在使用强与弱方面犯错。随着您对内存管理和对象生命周期越来越熟悉，您会发现需要/需要弱的情况。

【讨论】：