无法将数据传递给前一个视图控制器

Posted 2023-02-23

【中文标题】无法将数据传递给前一个视图控制器

【英文标题】：Unable to pass data to the previous viewcontroller

【发布时间】：2017-02-11 11:57:21

【问题描述】：

我正在尝试实现委托设计模式。

我有两个视图控制器如下m

CallViewViewController CEPeoplePickerNavigationController

这是我对CallViewViewController的接口定义

@interface CallViewViewController ()<CEPeoplePickerNavigationControllerDelegate>



@property(nonatomic)CustomMessageClass * customMessageClassObject;

@end

在我的实现中，我当然实现了委托方法

-(void)cePeoplePickerNavigationController:(CEPeoplePickerNavigationController *)peoplePicker didFinishPickingPeople:(NSArray *)peopleArg values:(NSDictionary *)valuesArg

    NSLog(@"can populate the tableview");

这是我第二个类的接口定义，

@protocol CEPeoplePickerNavigationControllerDelegate;

@interface CEPeoplePickerNavigationController : UIViewController <UITableViewDelegate,UITableViewDataSource>
    id<CEPeoplePickerNavigationControllerDelegate> peoplePickerDelegate;
    ABAddressBookRef addressBook;


@property (nonatomic, assign) id<CEPeoplePickerNavigationControllerDelegate> peoplePickerDelegate;
@property (nonatomic, retain) CEPeoplePickerNavigationController *ppnc;

@end


@protocol CEPeoplePickerNavigationControllerDelegate <NSObject>

- (void)cePeoplePickerNavigationController:(CEPeoplePickerNavigationController *)peoplePicker didFinishPickingPeople:(NSArray*)people values:(NSDictionary *)values;

@end

当用户按下提交按钮时，我正在执行以下代码，

 if ([self.ppnc.peoplePickerDelegate respondsToSelector:@selector(cePeoplePickerNavigationController:didFinishPickingPeople:values:)])
        [self.ppnc.peoplePickerDelegate cePeoplePickerNavigationController:self.ppnc didFinishPickingPeople:sortedPeople values:[NSDictionary dictionaryWithDictionary:self.selectedValues]]; 

但是数据没有被传回之前的视图控制器。为什么会这样？

更新

我尝试使用以下代码将表单首先移动到第二个视图控制器，

CEPeoplePickerNavigationController *nextVC = [self.storyboard instantiateViewControllerWithIdentifier:@"PeoplePickerNavigationController"];
    nextVC.peoplePickerDelegate = self;
    [self presentViewController:nextVC animated:YES completion:nil];

但它会引发以下错误，

由于未捕获的异常“NSInvalidArgumentException”而终止应用程序，原因：“-[UINavigationController setPeoplePickerDelegate:]：无法识别的选择器发送到实例 0x101054800”

【问题讨论】：

你的第一个视图控制器是否接受委托？

no...第一个视图控制器委托没有被调用

我正在使用 instantiateViewControllerWithIdentifier

我猜@Saheb Roy 给出了完整的解决方案

它正在使应用程序崩溃

【参考方案1】：

您只需要使用 Custom Delegate

传递数据

在您的 CEPeoplePickerNavigationController 的 .h 文件中写入以下代码

@class CEPeoplePickerNavigationController;

@protocol CEPeoplePickerNavigationController <NSObject>
- (void)previousViewController:(CEPeoplePickerNavigationController *)controller itemToSend:(NSString *)item;
@end

@interface CEPeoplePickerNavigationController : UIViewController

@property (nonatomic, weak) id < CEPeoplePickerNavigationController Delegate> delegate;

@end

在您移至上一个视图控制器事件时，您需要将代码放在下面

[self.delegate previousViewController:self itemToSend:@"From Previous VC"];
[self.navigationController popViewControllerAnimated:true];

在您的 CallViewViewController 上，您只需在 .m 文件中添加以下代码

#import "CEPeoplePickerNavigationController.h"

@interface ViewController ()< CEPeoplePickerNavigationController Delegate>

在前一个视图控制器上添加方法声明

- (void)previousViewController:(CEPeoplePickerNavigationController *)controller itemToSend:(NSString *)item

    NSLog(@"from CEPeoplePickerNavigationController %@",item);

确保当您导航到 CEPeoplePickerNavigationController 时，您需要将委托分配给 self，如下所示

CEPeoplePickerNavigationController *objVC = [self.storyboard instantiateViewControllerWithIdentifier:@"CEPeoplePickerNavigationController"];
objVC.delegate = self;
[self.navigationController pushViewController:infoController animated:YES];

【讨论】：

请检查***.com/questions/42197175/…

【参考方案2】：

当您从CallViewViewController 移动到CEPeoplePickerNavigationController 时，必须有某种导航，您正在推动或应用segue 以进入下一个VC。

只需在此处添加这行代码 -

如果你正在使用 segue --

CEPeoplePickerNavigationController *nextVC = [segue destinationViewController];
nextVC.peoplePickerDelegate = self;

如果您使用的是实例化 --

CEPeoplePickerNavigationController *nextVC = [self.storyboard instantiateWithStoryboardid:@"YOUR STORYBOARD ID"];
nextVC.peoplePickerDelegate = self;

一旦完成，它将响应来自下一个控制器的委托

编辑

请将您的 CEPeoplePickerNavigationController .h 代码清除为以下内容

 @protocol CEPeoplePickerNavigationControllerDelegate <NSObject>

 - (void)cePeoplePickerNavigationController:(CEPeoplePickerNavigationController *)peoplePicker didFinishPickingPeople:(NSArray*)people values:(NSDictionary *)values;

@end


@interface CEPeoplePickerNavigationController : UIViewController <UITableViewDelegate,UITableViewDataSource>
ABAddressBookRef addressBook;


@property (nonatomic, assign) id<CEPeoplePickerNavigationControllerDelegate> peoplePickerDelegate;
@property (nonatomic, retain) CEPeoplePickerNavigationController *ppnc;

@end

【讨论】：

我正在使用 instantiateViewControllerWithIdentifier

相应地编辑答案

应用在 nextVC.peoplePickerDelegate = self; 处显示错误；

发布了什么错误？并且请检查语法，因为我在 Windows 机器上发布了这个答案，所以我无法访问 Xcode 来自动更正语法，因为某些字符可能有点偏离

我已经用我遇到的错误更新了问题