Question

我遇到代理，协议问题，试图在两个视图控制器之间传递数据。

我能够传递数据，但是当我尝试更改用户输入时，通过将两个用户输入一起添加，然后传递该数据，我就会卡住。有人可以解释我犯错的地方吗？谢谢你。

如果这是一个新手问题，我很抱歉。但是我现在已经在努力了一段时间了。再次感谢你。

我的View Controller.m文件 #import“ViewController.h”

@interface ViewController ()

@end

@implementation ViewController

-(void)setTheValues
{
int numberOne = [_numberOne.text intValue];
int numberTwo = [_numberTwo.text intValue];
int sumTotal = (numberOne+numberTwo);
sumTotal = [_sumTotal.text intValue];
//  self.sumTotal.text = [NSString stringWithFormat:@"%d", sumTotal];
}

 -(void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
if([[segue identifier]isEqualToString:@"vc2"])
{
SecondViewController *vc2 = [segue destinationViewController];
NSString *passedMessage = _textField.text;
vc2.passedMessage = passedMessage;
    [self setTheValues];
    NSString *passedMessageTwo = _sumTotal.text;
    vc2.passedMessageTwo = passedMessageTwo;

}
}

 - (void)viewDidLoad
{
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.

 }

 - (void)didReceiveMemoryWarning
{
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
 }

 - (IBAction)sendOver:(UIButton *)sender {
  [self setTheValues];
}
 @end

查看Controller.h

#import <UIKit/UIKit.h>
#import "SecondViewController.h"

@interface ViewController : UIViewController <sendMessage>

- (IBAction)sendOver:(UIButton *)sender;

@property (weak, nonatomic) IBOutlet UITextField *textField;
@property (weak, nonatomic) IBOutlet UITextField *numberOne;
@property (weak, nonatomic) IBOutlet UITextField *numberTwo;

// declaring sumTotal
@property (weak, nonatomic) IBOutlet UILabel *sumTotal;
@end

我的第二个视图Controller.h #import

@protocol sendMessage <NSObject>

@end

@interface SecondViewController : UIViewController

- (IBAction)goBack:(UIButton *)sender;
@property (weak, nonatomic) IBOutlet UILabel *label;

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

//delegate property

@property(retain)id <sendMessage> delegate;
@property(nonatomic, strong)NSString *passedMessage;
@property(nonatomic, strong)NSString *passedMessageTwo;
@property(nonatomic, strong)NSString *passedMessageThree;

 @end

Answer 1

EDITED，基于danh发布的指出：

在我看来，你的setTheValues方法是错误的。这是您的（不正确的）代码：

-(void)setTheValues
{
  int numberOne = [_numberOne.text intValue];
  int numberTwo = [_numberTwo.text intValue];

  //This line adds the wales of the 2 strings. That's good.
  int sumTotal = (numberOne+numberTwo);

  //This line throws away the value from the last line 
  //and replaces it with the contents of _sumTotal. That's not right.
  sumTotal = [_sumTotal.text intValue];
}

最好这样做：

-(int) calcTotal;
{
  int numberOne = [_numberOne.text intValue];
  int numberTwo = [_numberTwo.text intValue];

  //This line adds the wales of the 2 strings. That's good.
  int sumTotal = (numberOne+numberTwo);
  return sumTotal;
}

然后重写prepareForSegue方法：

 -(void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
  if([[segue identifier]isEqualToString:@"vc2"])
  {
    SecondViewController *vc2 = [segue destinationViewController];

    vc2.delegate = self;

    NSString *passedMessage = _textField.text;
    vc2.passedMessage = passedMessage;

    //Call calcTotal to read the inputs and return their sum as an integer.
    int total = [self calcTotal];

    //convert the sum to a string.
    NSString *passedMessageTwo = [NSString stringWithFormat: "%d", total];
    vc2.passedMessageTwo = passedMessageTwo;
  }
}

顺便说一下，您的代码在您的属性上混合了“保留”和“强”/“弱”限定符。你不能这样做。 “保留”用于手动引用计数代码。 ARC中使用“强”和“弱”。如果你不使用ARC，你应该是。切换到ARC，然后将“保留”切换为非原子，强。

您还有一个“委托”属性（即那个被声明为保留的属性），您根本就没有设置或使用它。您应该在prepareForSegue方法中设置它

无法在视图控制器之间传递多个标签

1 个答案: