objective-c - 返回 null 的按钮数组

Question

我正在尝试将我创建的按钮添加到数组中，然后从数组中删除它们。我的数组一直返回 null，所以我感觉我的按钮甚至没有被添加到我的数组中？

我是初学者。我正在使用 Xcode 4.3。这是我的代码:

//
//  MainViewController.h
//  Test-Wards
//
//  Created by Dayle Pearson on 5/12/12.
//  Copyright (c) 2012 __MyCompanyName__. All rights reserved.
//

#import "FlipsideViewController.h"

@interface MainViewController : UIViewController <FlipsideViewControllerDelegate> 
{
    /*This stuff creates a timer */
    IBOutlet UILabel *opponentsBlue;
    NSTimer *timer;
    int redBlue;

    /*Stuff for making a label creator */
    CGPoint startPoint;
    int xStuff, yStuff;

    /*array for storing wards*/
    NSMutableArray *wardArray;

}

@property CGPoint startPoint;

- (IBAction)startRedBlue:(id)sender;

- (IBAction)removeWard:(id)
sender;
- (void)countdown;

@end

//
//  MainViewController.m
//  Test-Wards
//
//  Created by Dayle Pearson on 5/12/12.
//  Copyright (c) 2012 __MyCompanyName__. All rights reserved.
//

#import "MainViewController.h"

@interface MainViewController ()

@end

@implementation MainViewController

@synthesize startPoint;

- (void)countdown 
{
    if (redBlue < 2) {

        [timer invalidate];
        timer = nil;
    }
    redBlue -= 1;
    opponentsBlue.text = [NSString stringWithFormat:@"%i", redBlue];
}

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
    UITouch *theTouch = [touches anyObject];
    startPoint = [theTouch locationInView:self.view];

}


- (IBAction)startRedBlue:(id)sender 
{
    UIButton *wardButton = [UIButton buttonWithType:UIButtonTypeRoundedRect];
    wardButton.frame = CGRectMake((startPoint.x - 5), (startPoint.y - 5), 10, 10);
    [wardButton setTitle:@"180" forState:UIControlStateNormal];
    //add targets and actions
    /*[wardButton addTarget:self action:@selector() forControlEvents:<#(UIControlEvents)#>*/
    //add to a view
    [self.view addSubview:wardButton];

    [self->wardArray addObject: wardButton];
    NSLog(@"This elemnt = %@", wardArray);


}
- (IBAction)removeWard:(id)sender 
{
    [self->wardArray removeLastObject];    
}
- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
}

- (void)viewDidUnload
{
    [super viewDidUnload];
    // Release any retained subviews of the main view.
}

- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation
{
    return (interfaceOrientation != UIInterfaceOrientationPortraitUpsideDown);
}

#pragma mark - Flipside View

- (void)flipsideViewControllerDidFinish:(FlipsideViewController *)controller
{
    [self dismissModalViewControllerAnimated:YES];
}

- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
    if ([[segue identifier] isEqualToString:@"showAlternate"]) {
        [[segue destinationViewController] setDelegate:self];
    }
}

@end

Answer 1

您忘记初始化您的 wardArray。你应该添加

wardArray = [NSMutableArray array];

到您指定的初始化程序。

在 Objective-C 中，向 nil 对象发送消息是合法的——这些消息会被简单地忽略。这就是为什么您看不到您添加的项目的原因。

我还注意到您向 View 添加了按钮，但从未删除它们。要从屏幕上删除按钮，请按如下方式更改代码:

 - (IBAction)removeWard:(id)sender 
{
    [[self->wardArray lastObject] removeFromSuperview];
    [self->wardArray removeLastObject];    
}