Question

我在Xcode中打开了一个简单的iPhone项目。在storyboard文件中，我有一个视图控制器： 2个文本字段 1个标签 1个圆形矩形按钮

我要做的是以下内容：让用户在字段A中输入任意数字，然后在字段B中输入相同的数字。然后，一旦按下“提交”按钮，我希望应用程序添加这两个值。

到目前为止，这是我所拥有的代码，但我目前陷入困境，因为我在构建时遇到错误。

我的页眉文件：

#import <UIKit/UIKit.h>



@interface ADDViewController : UIViewController



@property (copy,nonatomic) NSString *valueA;

@property (copy,nonatomic) NSString *valueB;



@end

我的实施档案：

#import "ADDViewController.h"



@interface ADDViewController ()

- (IBAction)submitButton:(id)sender;

@property (weak, nonatomic) IBOutlet UITextField *numberA;

@property (weak, nonatomic) IBOutlet UITextField *numberB;

@property (weak, nonatomic) IBOutlet UILabel *answerLabel;



@end



@implementation ADDViewController



- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil

{

    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];

    if (self) {

        // Custom initialization

    }

    return self;

}



- (void)viewDidLoad

{

    [super viewDidLoad];

     // Do any additional setup after loading the view.

}



- (void)didReceiveMemoryWarning

{

    [super didReceiveMemoryWarning];

    // Dispose of any resources that can be recreated.

}



- (IBAction)submitButton:(id)sender {



    self.valueA = self.numberA.text;

    self.valueB = self.numberB.text;



// THE FOLLOWING IS WHERE I AM CURRENTLY GETTING AN ERROR WITH XCODE: 
// XCODE SAYS : INVALID OPERANDS TO BINARY EXPRESSION ('NSSTRING *' AND 'NSSTRING *')

    NSString * total = self.valueA + self.valueB;

}

@end

这是我的故事板文件的屏幕截图：

http://i43.tinypic.com/352q98i.jpg

提前谢谢！

Answer 1

您必须将字符串转换为数字（例如，使用intValue或floatValue方法），添加这两个数字，然后将生成的sum转换回字符串。您无法对字符串执行数字操作。

因此，您可以执行以下操作：

CGFloat a = [self.numberA.text floatValue];
CGFloat b = [self.numberB.text floatValue];
CGFloat sum = a + b;
NSNumberFormatter *formatter = [[NSNumberFormatter alloc] init];
formatter.numberStyle = NSNumberFormatterDecimalStyle;
self.answerLabel.text = [formatter stringFromNumber:@(sum)];

如何在Objective-C中创建简单的添加？

1 个答案: