选择器中的第二个组件未正确实例化

Question

正在使用选择器开发简单的实用程序应用程序，但消息未正确输出。第二个组件没有输出“我正在睡觉并且对此感到高兴”之类的内容，而是没有正确实例化，而是输出“我正在睡觉并且对此感到 InstatwitViewController ”。

一切都已在 IB 中连接起来。

你能告诉我出了什么问题吗？

这是 .h 文件：

#import <UIKit/UIKit.h>

@interface InstatwitViewController : UIViewController
<UIPickerViewDataSource, UIPickerViewDelegate>
{
    IBOutlet UIPickerView *tweetPicker;
    NSArray* activities;
    NSArray* feelings;
}

@property (nonatomic,retain)UIPickerView* tweetPicker; 
- (IBAction) sendButtonTapped:(id)sender;

@end

这是实现文件：

#import "InstatwitViewController.h"

@implementation InstatwitViewController
@synthesize tweetPicker;



/*
// The designated initializer. Override to perform setup that is required before the view is loaded.
- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil {
    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
    if (self) {
        // Custom initialization
    }
    return self;
}
*/

/*
// Implement loadView to create a view hierarchy programmatically, without using a nib.
- (void)loadView {
}
*/

- (NSInteger)numberOfComponentsInPickerView:(UIPickerView *)pickerView 
    {
        return 2;
    }

- (NSInteger)pickerView:(UIPickerView *)pickerView numberOfRowsInComponent:(NSInteger)component
    {
        if (component==0) {
            return [activities count];
        }
        else
            return [feelings count];
    }





// Implement viewDidLoad to do additional setup after loading the view, typically from a nib.
- (void)viewDidLoad {
    activities = [[NSArray alloc] initWithObjects:@"sleeping", @"eating", @"working", @"thinking", @"crying", @"begging", @"leaving", @"shopping", @"hello worlding", nil];
    feelings = [[NSArray alloc] initWithObjects:@"awesome", @"sad", @"happy", @"ambivalent", @"nauseous", @"psyched",@"confused", @"hopeful", @"anxious", nil];
    [super viewDidLoad];
}



/*
// Override to allow orientations other than the default portrait orientation.
- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation {
    // Return YES for supported orientations
    return (interfaceOrientation == UIInterfaceOrientationPortrait);
}
*/

- (void)didReceiveMemoryWarning {
    // Releases the view if it doesn't have a superview.
    [super didReceiveMemoryWarning];

    // Release any cached data, images, etc that aren't in use.
}

- (NSString *)pickerView:(UIPickerView *)pickerView titleForRow:(NSInteger)row forComponent:(NSInteger)component
{
    switch (component){
        case 0:
            return [activities objectAtIndex:row];
        case 1:
            return [feelings objectAtIndex:row];
    }
    return nil;
}

- (IBAction) sendButtonTapped:(id)sender
{
    NSString* themessage = [NSString stringWithFormat:@"I'm %@ and feeling %@ about it.",
                            [activities objectAtIndex:[tweetPicker selectedRowInComponent:0]]];
                            [feelings objectAtIndex:[tweetPicker selectedRowInComponent:1]];
    NSLog(themessage);
}

- (void)viewDidUnload {
    // Release any retained subviews of the main view.
    // e.g. self.myOutlet = nil;
}


- (void)dealloc {
    [tweetPicker release];
    [activities release];
    [feelings release];
    [super dealloc];
}

@end

Answer 1

如果我们修复缩进，您的 sendButtonTapped: 看起来像这样：

- (IBAction) sendButtonTapped:(id)sender
{
    NSString* themessage = [NSString stringWithFormat:@"I'm %@ and feeling %@ about it.",
                            [activities objectAtIndex:[tweetPicker selectedRowInComponent:0]]];
    [feelings objectAtIndex:[tweetPicker selectedRowInComponent:1]];
    NSLog(themessage);
}

换句话说，您的方括号嵌套错误，导致您永远无法将“感觉”传递给格式字符串。你很“幸运”，它没有撞到你身上。