Question

确定。我有一个“游戏”类，它创建了我的班级“Board”的实例，并测试它。

“Board”类有一个字典，似乎某种程度上无法保持它的值（？）试图将代码绑定到最小：

游戏课程：

@interface Game : UIViewController{
    Board *board;
}
-(void)testAgain; 

@implementation Game
-(void)setup{
    board = [Board alloc]createBoard];
    [board test]; //returns right value
    [self testAgain]; //returns (null), see output below
}
-(void)testAgain{
    [board test];
}

-(void)didLoad{
    [self setup];
}

董事会成员：

@interface Board : NSObject{
@property(nonatomic, retain) NSMutableDictionary *dict;

-(Board *)createBoard;
-(void)test;

@implementation Board
@synthesize dict;

-(Board *)createBoard{

    dict = [[NSMutableDictionary alloc]init];

    [dict setObject:@"foo1" forKey:@"1"];
    [dict setObject:@"foo2" forKey:@"2"];
    [dict setObject:@"foo3" forKey:@"3"];
    [dict setObject:@"foo4" forKey:@"4"];
    [dict setObject:@"foo5" forKey:@"5"];

    return self;
}

-(void)test{
    NSLog(@"Test return: %@", [dict objectForKey:@"4"]);
}

以下输出：

2012-06-23 01:05:28.614 Game[21430:207] Test return: foo4
2012-06-23 01:05:32.539 Game[21430:207] Test return: (null)

提前，谢谢你的帮助！

Answer 1

@implementation Game
-(void)setup{
    board = [[[Board alloc] init] createBoard];
    [board test]; //returns right value
    [self testAgain]; //returns (null), see output below
}

您正在使用的创建模式超出了Objective-C中的每个约定。您应该使用[Board new]，[[Board alloc] init | With ... |]或[Board board | With ... |]。

-(Board *)createBoard {

    self.dict = [[NSMutableDictionary alloc]init];

    [dict setObject:@"foo1" forKey:@"1"];
    [dict setObject:@"foo2" forKey:@"2"];
    [dict setObject:@"foo3" forKey:@"3"];
    [dict setObject:@"foo4" forKey:@"4"];
    [dict setObject:@"foo5" forKey:@"5"];
}

让我们看看你的代码是否能更好地运行，重新安装了丢失的init所在的位置以及那个缺少自我的东西。

Answer 2

首先，您没有使用Board正确初始化createBoard对象。您甚至没有在该方法中返回Board对象。尝试将该方法修改为以下内容：

-(id)initWithCreatedBoard {

self = [super init];


if (self) { 

dict = [[NSMutableDictionary alloc]init];

[dict setObject:@"foo1" forKey:@"1"];
[dict setObject:@"foo2" forKey:@"2"];
[dict setObject:@"foo3" forKey:@"3"];
[dict setObject:@"foo4" forKey:@"4"];
[dict setObject:@"foo5" forKey:@"5"];

[dict retain];

}

返回自我;

}

您也可能想要retain dict。因为他们可能会被解除分配。

另外，你使用ARC吗？

另一件事，而不是有两个方法testAgain和test。只需拨打test两次：

for (int i = 0; i <= 2; i++) {

[self test];

}

只是更好的结构，就是这样。请反馈您的结果！

NSMutableDictionary返回（null）有效键/忘记它的值？

2 个答案: