ios - 对象自动设置为零

Question

首先是我的代码:

- (void)viewDidLoad {
    [super viewDidLoad];

    self.elements = [NSMutableArray arrayWithObjects:@"Object 1", @"Object 2", @"Object 3", nil];
    self.elements2 = @"Lorem ipsum";
    NSLog(@"%@", self.elements);

    [self loadContent];
}

他打印出，_elements 在 loadContent 之后也被正确初始化，_elements 包含三个对象。但是在 viewDidLoad 方法之后直接调用的 numberOfComponentsInPickerView: 方法后面只有几行，_elements 是 nil。我不知道为什么我的应用程序将 _elements 设置为 nil？

谢谢 iComputerfreak

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编辑

我将我的完整代码上传到 gist.github: https://gist.github.com/iComputerfreak/fa3d3ee925c45cd6e1f2

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控制台输出

好的，这里是我的控制台输出:

// in viewDidLoad (after setting): 
2014-05-13 16:56:14.292 HFG Vertretungsplan[1051:60b] (
    "Object 1",
    "Object 2",
    "Object 3"
)
// numberOfComponents called automatically:
2014-05-13 16:56:14.298 HFG Vertretungsplan[1051:60b] numberOfComponentsInPickerView: (null)
2014-05-13 16:56:14.303 HFG Vertretungsplan[1051:60b] numberOfComponentsInPickerView: (null)
// viewWillAppear method reached:
2014-05-13 16:56:14.306 HFG Vertretungsplan[1051:60b] View will appear
2014-05-13 16:56:14.306 HFG Vertretungsplan[1051:60b] Elements in viewWillAppear: ( // NSLog("%@", self.elements);
    "Object 1",
    "Object 2",
    "Object 3"
)
// [self.elementsPicker reloadAllComponents];
2014-05-13 16:56:14.307 HFG Vertretungsplan[1051:60b] numberOfComponentsInPickerView: (null)
2014-05-13 16:56:14.308 HFG Vertretungsplan[1051:60b] Elements after reloadAllComponents: (
    "Object 1",
    "Object 2",
    "Object 3"
)

所以只有在重新加载组件时元素才为零。前后都有内容。

Answer 1

覆盖你的_elements getter

- (NSMutableArray *)elements
{
    if (!_elements)
        _elements = [[NSMutableArray alloc] init];
    return _elements;
}

第一次调用_elements就像

self.elements