Question

我在RootViewController中初始化了一个数组，并将一个方法添加到数组中。我在SecondViewController中创建了一个RootViewController对象。该方法运行（输出消息），但它不向数组添加任何内容，并且数组似乎为空。代码在下面，有什么建议吗？

RootViewController.h

#import "RootViewController.h"
#import "SecondViewController.h"

@implementation RootViewController
- (void)viewDidLoad {
    [super viewDidLoad];
    myArray2 = [[NSMutableArray alloc] init];

    NSLog(@"View was loaded");
}
-(void)addToArray2{
    NSLog(@"Array triggered from SecondViewController");
    [myArray2 addObject:@"Test"];
    [self showArray2];
}

-(void)showArray2{
    NSLog(@"Array Count: %d", [myArray2 count]);
}
-(IBAction)switchViews{
    SecondViewController *screen = [[SecondViewController alloc] initWithNibName:nil bundle:nil];
    screen.modalTransitionStyle = UIModalTransitionStyleCoverVertical;
    [self presentModalViewController:screen animated:YES];
    [screen release];
}

SecondViewController.m

#import "SecondViewController.h"
#import "RootViewController.h"

@implementation SecondViewController

-(IBAction)addToArray{

    RootViewController *object = [[RootViewController alloc] init];
    [object addToArray2];

}
-(IBAction)switchBack{
    [self dismissModalViewControllerAnimated:YES];
}

EDIT *************

使用Matt的代码我收到以下错误：

“'RootViewController'之前的预期说明符限定符列表”

Answer 1

你在这里缺少一些非常重要的基础知识。如果在SecondViewController中分配新的RootViewController，它与用于创建SecondViewController的实例不同，因此它不会引用要添加对象的数组。你想做什么是行不通的。您必须在SecondViewController中为RootViewController创建一个ivar，然后在第二个视图中访问它。像这样：

-(IBAction)switchViews{
    SecondViewController *screen = [[SecondViewController alloc] 
                                       initWithNibName:nil bundle:nil];
    screen.modalTransitionStyle = UIModalTransitionStyleCoverVertical;
    [screen setRootViewController:self];
    [self presentModalViewController:screen animated:YES];
    [screen release];
}

你的ivar需要在SecondViewController.h中声明：

@property (nonatomic, retain) RootViewController *rootViewController;

然后在.m

中合成

然后，您可以从SecondViewController中访问ivar：

-(IBAction)addToArray{
    [[self rootViewController] addToArray2];
}

RootViewController中的方法不存储数组

1 个答案: