传递变量和切换视图 iOS/Xcode

Question

所以，我对 iOS/Obj-C 和 Xcode 非常陌生，我正在尝试通过构建一个简单的选项卡式视图应用程序来学习，该应用程序采用一些用户变量，将用户移动到下一个视图并显示变量。

目前，我有第一个视图 - 用户选择两个日期。我已成功将这两个日期记录到控制台。我还不太明白在视图之间移动的概念。

我需要帮助的是 - 在 - (IBAction)submitDates 函数中，将用户移动到下一个视图并将变量也传递到该视图 - 并将变量记录到控制台。

注意：第二个视图文件（JPSecondViewController.m 和 JPSecondViewController.h 尚未触及）。

提前非常感谢任何帮助/指导！

我的 JPFirstViewController.m 文件

//  JPFirstViewController.m
//  Vacay
//

#import "JPFirstViewController.h"
#import "JPSecondViewController.h"

@interface JPFirstViewController ()

@end

@implementation JPFirstViewController

- (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)submitDates {


    //Save the selected date variables
    NSDate *dateFromPicker = [_fromDate date];
    NSDate *endDateFromPicker = [_endDate date];
    NSLog(@"From date: %@ and end date: %@", dateFromPicker, endDateFromPicker);

    //Move user to second view controller

}

@end

我的 JPFirstViewController.m 文件

//  JPFirstViewController.h
//  Vacay
/

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

@interface JPFirstViewController : UIViewController
@property (strong, nonatomic) IBOutlet UIDatePicker *endDate;
@property (strong, nonatomic) IBOutlet UIDatePicker *fromDate;
- (IBAction)submitDates;

@end

Answer 1

有几种传递变量的方法，这里是最简单的一种。

- (IBAction)submitDates {
    //Save the selected date variables
    NSDate *dateFromPicker = [_fromDate date];
    NSDate *endDateFromPicker = [_endDate date];
    NSLog(@"From date: %@ and end date: %@", dateFromPicker, endDateFromPicker);

    //Create an instance of the second view controller
    // If you are using NIBs
    JPSecondViewController *secondViewController = [[JPSecondViewController alloc] init];

    //// If you are using storyboards, then you will need to know what the storyboard identifier is for JPSecondViewController. 
    //NSString *identifier = @"<Second Storyboard Identifier>";
    //JPSecondViewController *secondViewController = [self.storyboard instantiateViewControllerWithIdentifier:identifier];

    //Fill in all the data need for the second view controller
    secondViewController.fromDate = dateFromPicker;
    secondViewController.endDate = endDateFromPicker;

    //Show the second view controller
    // Option 1: Add the second view controller to a navigation controller
    [self.navigationController pushViewController:secondViewController animated:YES];

    //// Option 2: Show the second view controller as a modal view controller
    //[self presentViewController:secondViewController animated:YES completion:nil];
}

这将创建第二个视图控制器填充值并以两种方式之一呈现第二个视图控制器。如果第一个视图控制器嵌入在导航控制器中，那么您只需将第二个视图控制器添加到导航堆栈。如果第一个视图控制器不在导航控制器中，则将其呈现为模式。

Answer 2

您可以使用多种方法在类之间传递变量

1. 单身人士（我更喜欢）
2. NSUserDefaults