为啥这个 NSMutableArray 没有被填充？

Posted 2023-02-24

【中文标题】为啥这个 NSMutableArray 没有被填充？

【英文标题】：Why isn't this NSMutableArray getting populated?为什么这个 NSMutableArray 没有被填充？

【发布时间】：2010-08-27 01:38:55

【问题描述】：

我有一个NSMutableArray 我正在尝试使用for-loop 填充并为它制作NSStrings。这些将成为我的UIPickerView 的数据源。您会看到一些注释掉的行，其中我手动创建了 NSArrays 并且它们显示得很好，但是我的 for-loop NSMutableArray 似乎不接受我正在制作的字符串。 NSLogs 表明我正在制作字符串（以及等效的 float），但是从 NSMutableArray 中提取值的 NSLogs 显示为 null 和 0.0

界面...

---

//  PoolSizePickerViewController.h

#import <UIKit/UIKit.h>
#define kLengthComponent 0
#define kWidthComponent 1
#define kDepthComponent 2

@protocol PoolSizePickerViewControllerDelegate;

@interface PoolSizePickerViewController : UIViewController <UIPickerViewDelegate, UIPickerViewDataSource> 
    UIPickerView *poolSizePicker;
    float length, width, depth;
    NSMutableArray *lengthStrings, *widthStrings, *depthStrings;
    NSMutableArray *lengthFloats, *widthFloats, *depthFloats;
    NSString *pickerType;
    NSString *pickerDescription;
    UIButton *selectButton;
    UIButton *cancelButton;
    UILabel *pickerTitleLabel;
    UITextView *pickerDescriptionLabel;
    id <PoolSizePickerViewControllerDelegate> delegate;


@property (nonatomic, retain) IBOutlet UIPickerView *poolSizePicker;
@property float length, width, depth;
@property (nonatomic, retain) NSMutableArray *lengthStrings, *widthStrings, *depthStrings;
@property (nonatomic, retain) NSMutableArray *lengthFloats, *widthFloats, *depthFloats;
@property (nonatomic, retain) NSString *pickerType;
@property (nonatomic, retain) NSString *pickerDescription;
@property (nonatomic, retain) IBOutlet UIButton *selectButton;
@property (nonatomic, retain) IBOutlet UIButton *cancelButton; 
@property (nonatomic, retain) IBOutlet UILabel *pickerTitleLabel;
@property (nonatomic, retain) IBOutlet UITextView *pickerDescriptionLabel;
@property (assign) id <PoolSizePickerViewControllerDelegate> delegate;

- (IBAction)selectedSelectButton;
- (IBAction)selectedCancelButton;

@end

@protocol PoolSizePickerViewControllerDelegate <NSObject>

@optional

- (void)poolSizePickerViewController:(PoolSizePickerViewController *)controller 
                 didSelectLength:(float)length
                        andWidth:(float)width 
                        andDepth:(float)depth;

- (void)poolSizePickerViewController:(PoolSizePickerViewController *)controller 
               didSelectCancel:(BOOL)didCancel;

@end

---

以及实现...

---

//  PoolSizePickerViewController.m

#import "PoolSizePickerViewController.h"

@implementation PoolSizePickerViewController

@synthesize poolSizePicker;
@synthesize length, width, depth;
@synthesize lengthStrings, widthStrings, depthStrings;
@synthesize lengthFloats, widthFloats, depthFloats;
@synthesize delegate;
@synthesize pickerType, pickerDescription;
@synthesize selectButton, cancelButton;
@synthesize pickerTitleLabel;
@synthesize pickerDescriptionLabel;

- (IBAction)selectedSelectButton 
    NSInteger lengthRow = [poolSizePicker selectedRowInComponent:kLengthComponent];
    NSInteger widthRow = [poolSizePicker selectedRowInComponent:kWidthComponent];
    NSInteger depthRow = [poolSizePicker selectedRowInComponent:kDepthComponent];
    length = [[self.lengthFloats objectAtIndex:lengthRow] floatValue];
    width = [[self.widthFloats objectAtIndex:widthRow] floatValue];
    depth = [[self.depthFloats objectAtIndex:depthRow] floatValue];
    if ([self.delegate respondsToSelector:@selector (poolSizePickerViewController:didSelectLength:andWidth:andDepth:)]) 
        [self.delegate poolSizePickerViewController:self didSelectLength:length andWidth:width andDepth:depth];
    


- (IBAction)selectedCancelButton 
    if ([self.delegate respondsToSelector:@selector (poolSizePickerViewController:didSelectCancel:)]) 
        [self.delegate poolSizePickerViewController:self didSelectCancel:YES];
    



- (void)viewDidLoad 
    for (int footIndex = 6; footIndex < 40; footIndex ++) 
        for (int inchIndex = 0; inchIndex < 2; inchIndex ++) 
            [self.lengthStrings addObject:[NSString stringWithFormat:@"   %d' %d\"", footIndex, inchIndex * 6]];
            NSLog(@"   %d' %d\"", footIndex, inchIndex * 6);
            NSLog(@"   -%@", [self.lengthStrings objectAtIndex:footIndex - 6]);
            [self.lengthFloats addObject:[NSNumber numberWithFloat:(float)footIndex + (float)inchIndex * 0.5f]];
            NSLog(@"   %1.1f", (float)footIndex + (float)inchIndex * 0.5f);
            NSLog(@"   -%1.1f", [[self.lengthFloats objectAtIndex:footIndex - 6] floatValue]);
        
    
    for (int footIndex = 6; footIndex < 40; footIndex ++) 
    for (int inchIndex = 0; inchIndex < 2; inchIndex ++) 
            [self.widthStrings addObject:[NSString stringWithFormat:@"   %d' %d\"", footIndex, inchIndex * 6]];
            [self.widthFloats addObject:[NSNumber numberWithFloat:(float)footIndex + (float)inchIndex * 0.5f]];
        
    
    for (int footIndex = 1; footIndex < 16; footIndex ++) 
        for (int inchIndex = 0; inchIndex < 2; inchIndex ++) 
            [self.depthStrings addObject:[NSString stringWithFormat:@"   %d' %d\"", footIndex, inchIndex * 6]];
            [self.depthFloats addObject:[NSNumber numberWithFloat:(float)footIndex + (float)inchIndex * 0.5f]];
        
    

//  lengthStrings = [NSArray arrayWithObjects:@"   6' 0\"", nil];
//  lengthFloats = [NSArray arrayWithObjects:[NSNumber numberWithFloat:1.0], nil];
//  widthStrings = [NSArray arrayWithObjects:@"   6' 0\"", nil];
//  widthFloats = [NSArray arrayWithObjects:[NSNumber numberWithFloat:2.0], nil];
//  depthStrings = [NSArray arrayWithObjects:@"   1' 0\"", nil];
//  depthFloats = [NSArray arrayWithObjects:[NSNumber numberWithFloat:3.0], nil];

    UIImage *buttonImageNormal = [UIImage imageNamed:@"whiteButton.png"];
    UIImage *stretchableButtonImageNormal = [buttonImageNormal stretchableImageWithLeftCapWidth:12 topCapHeight:0];
    [selectButton setBackgroundImage:stretchableButtonImageNormal forState:UIControlStateNormal];
    [cancelButton setBackgroundImage:stretchableButtonImageNormal forState:UIControlStateNormal];
    UIImage *buttonImagePressed = [UIImage imageNamed:@"blueButton.png"];
    UIImage *stretchableButtonImagePressed = [buttonImagePressed stretchableImageWithLeftCapWidth:12 topCapHeight:0];
    [selectButton setBackgroundImage:stretchableButtonImagePressed forState:UIControlStateHighlighted];
    [cancelButton setBackgroundImage:stretchableButtonImagePressed forState:UIControlStateHighlighted];
    pickerTitleLabel.text = [NSString stringWithFormat:@"Select a Pool %@", pickerType];
    pickerDescriptionLabel.text = self.pickerDescription;
    self.poolSizePicker.showsSelectionIndicator = YES;
    [super viewDidLoad];


- (void)didReceiveMemoryWarning 
    [super didReceiveMemoryWarning];


- (void)viewDidUnload 
    [super viewDidUnload];


- (void)dealloc 
    [super dealloc];


   #pragma mark -
   #pragma mark Picker Data Source Methods

- (NSInteger)numberOfComponentsInPickerView:(UIPickerView *)pickerView 
return 3;


- (NSInteger)pickerView:(UIPickerView *)pickerView numberOfRowsInComponent:(NSInteger)component 
    switch (component) 
        case kLengthComponent:
            return [self.lengthStrings count];
            break;
        case kWidthComponent:
            return [self.widthStrings count];
            break;
        default:
            return [self.lengthStrings count];
            break;
    


#pragma mark Picker Delegate Methods

- (NSString *)pickerView:(UIPickerView *)pickerView
         titleForRow:(NSInteger)row
        forComponent:(NSInteger)component 
    switch (component) 
        case kLengthComponent:
            return [self.lengthStrings objectAtIndex:row];
            break;
        case kWidthComponent:
            return [self.widthStrings objectAtIndex:row];
            break;
        default:
            return [self.depthStrings objectAtIndex:row];
            break;
    


@end

【参考方案1】：

您是否正在某个地方初始化您的数组？我在任何地方都看不到[[NSMutableArray alloc] init]。向 null 对象发送消息是无操作的，因此这些 addObjects 很可能被发送到 null 并且没有做任何事情。

【讨论】：

这是有道理的。我已经尽可能少地让自己适应alloc！但是它是如何与手动数组一起工作的呢？ [NSMutableArray addObject:] 与 [NSArray arrayWithObjects:] 有什么不同吗？ @property (nonatomic, retain) 不会初始化它们吗？我会在viewDidLoad 中尝试alloc 和init，然后在dealloc 中释放它们...

@Steve，[NSArray arrayWithObjects:] 等于 [[[NSArray alloc] initWithObjects:] autorelease]。

男孩，我希望有关于自动发布内容的参考！我在 Apple 文档中花了很多时间，但我没有提到那里的自动发布状态。谢谢！

大多数东西都是自动释放的，除非方法名称包括 init、new 或 copy。

这里有自动发布的参考，检查：developer.apple.com/mac/library/documentation/cocoa/conceptual/…