ios - 如何在 segue 中传递对象而不是对象的细节？

Question

我有一个简单的笔记应用程序，其中只有 2 个 View Controller :

1. TableView Controller - 列出所有笔记。
2. View Controller - 创建新笔记。

在 TableView Controller 中，我有一个从单元格返回到创建页面的 segue，用户可以在该页面编辑此特定单元格中的注释。

但我的问题是，当我对某个单元格(注释)进行编辑时，我正在创建一个包含我编辑内容的新注释...

因此，我需要传递笔记对象，而不是在 prepareForSegue 方法中传递笔记内容...

我该怎么做？

这是我的类(class):

NMNote:(正确地只包含 *content 的属性，稍后将添加更多行为)

#import <Foundation/Foundation.h>

@interface NMNote : NSObject

@property (strong, nonatomic) NSString *content;


@end

NMCreateNotesViewController.h:

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

@interface NMCreateNotesViewController : UIViewController 

@property (strong, nonatomic) NMNote *note;

@property (weak, nonatomic) IBOutlet UITextView *textField;

@property (strong, nonatomic) NSString *passedInString;


@end

NMCreateNotesViewController.m:

#import "NMCreateNotesViewController.h"
#import "NMNotesListViewController.h"


@interface NMCreateNotesViewController () <UITextViewDelegate>


@property (weak, nonatomic) IBOutlet UIBarButtonItem *saveButton;


@end



@implementation NMCreateNotesViewController


- (void)viewWillAppear:(BOOL)animated
{
    [super viewWillAppear:animated];

    // listen for keyboard hide/show notifications so we can properly adjust the table's height
    [[NSNotificationCenter defaultCenter] addObserver:self
                                             selector:@selector(keyboardWillShow:)
                                                 name:UIKeyboardWillShowNotification
                                               object:nil];
    [[NSNotificationCenter defaultCenter] addObserver:self
                                             selector:@selector(keyboardWillHide:)
                                                 name:UIKeyboardWillHideNotification
                                               object:nil];
}


#pragma mark - Notifications


- (void)adjustViewForKeyboardReveal:(BOOL)showKeyboard notificationInfo:(NSDictionary *)notificationInfo
{
    // the keyboard is showing so ƒ the table's height
    CGRect keyboardRect = [[notificationInfo objectForKey:UIKeyboardFrameEndUserInfoKey] CGRectValue];
    NSTimeInterval animationDuration =
    [[notificationInfo objectForKey:UIKeyboardAnimationDurationUserInfoKey] doubleValue];
    CGRect frame = self.textField.frame;

    // the keyboard rect's width and height are reversed in landscape
    NSInteger adjustDelta = UIInterfaceOrientationIsPortrait(self.interfaceOrientation) ? CGRectGetHeight(keyboardRect) : CGRectGetWidth(keyboardRect);

    if (showKeyboard)
        frame.size.height -= adjustDelta;
    else
        frame.size.height += adjustDelta;

    [UIView beginAnimations:@"ResizeForKeyboard" context:nil];
    [UIView setAnimationDuration:animationDuration];
    self.textField.frame = frame;
    [UIView commitAnimations];
}



- (void)keyboardWillShow:(NSNotification *)aNotification
{
    [self adjustViewForKeyboardReveal:YES notificationInfo:[aNotification userInfo]];
}



- (void)keyboardWillHide:(NSNotification *)aNotification
{
    [self adjustViewForKeyboardReveal:NO notificationInfo:[aNotification userInfo]];
}



- (void) prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
    if (sender != self.saveButton) return;
    if (self.textField.text.length > 0) {
        self.note = [[NMNote alloc] init];
        self.note.content = self.textField.text;

    }
}



- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
    if (self) {
        // Custom initialization
    }
    return self;
}



- (void)viewDidLoad
{
    [super viewDidLoad];
    if (self.passedInString != nil) {
        self.textField.text = self.passedInString;
    }
    // Do any additional setup after loading the view.
}



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

@end

NMNotesListViewController.h:

#import <UIKit/UIKit.h>

@interface NMNotesListViewController : UITableViewController

- (IBAction) unwindToList: (UIStoryboardSegue *) segue;

@end

NMNotesListViewController.m:

#import "NMNotesListViewController.h"
#import "NMCreateNotesViewController.h"

@interface NMNotesListViewController ()

@property (strong, nonatomic) NSMutableArray *notes;

@end

@implementation NMNotesListViewController



- (IBAction) unwindToList: (UIStoryboardSegue *) segue
{

    NMCreateNotesViewController *source = [segue sourceViewController];
    NMNote *note = source.note;

    if (note != nil) {
        [self.notes addObject:note];
        [self.tableView reloadData];
    }

}

- (id)initWithStyle:(UITableViewStyle)style
{
    self = [super initWithStyle:style];
    if (self) {
        // Custom initialization
    }
    return self;
}

- (void)viewDidLoad
{
    [super viewDidLoad];

    self.notes = [[NSMutableArray alloc] init];

    // Uncomment the following line to preserve selection between presentations.
    // self.clearsSelectionOnViewWillAppear = NO;

    // Uncomment the following line to display an Edit button in the navigation bar for this view controller.
    // self.navigationItem.rightBarButtonItem = self.editButtonItem;
}

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

#pragma mark - Table view data source

- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
{
    // Return the number of sections.
    return 1;
}

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
    // Return the number of rows in the section.
    return [self.notes count];
}

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    static NSString *CellIdentifier = @"NotesPrototypeCell";
    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier forIndexPath:indexPath];

    // Configure the cell...


    NMNote *note = [self.notes objectAtIndex:indexPath.row];
    cell.textLabel.text = note.content;


    return cell;
}


- (void) prepareForSegue:(UIStoryboardSegue *)segue sender:(UITableViewCell *)sender

{
    if ([[segue identifier] isEqualToString:@"noteSegue"]) {
        NMCreateNotesViewController *destination = [segue destinationViewController];
        NSInteger indx = [self.tableView indexPathForCell:sender].row;
        NMNote *note = self.notes[indx];
        destination.passedInString = note.content;
    }
}

//#pragma mark - delegate
//
//- (void) tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
//{
//    
//}

@end

这是屏幕流程:

初始 View 是这个 TableView :

现在有你写笔记的 TextView:

现在，保存笔记后，您将返回到第一个屏幕。然后你可以点击一个填充的单元格，你将返回到这个屏幕(带有 TextView 的那个)，这样你就可以编辑它了。但是它不会编辑它，而是会使用编辑后的内容创建一个新的。像这样:

拜托，我将不胜感激任何帮助来完成我的任务..谢谢!

Answer 1

当你将笔记传递给 NMCreateNotesViewController 时，你需要做的是区分编辑和添加操作，这样当你返回到 TableView 时，你可以用新编辑的条目替换旧条目, 或添加新条目。

我采用的方法是使用两个转场，一个来自 + 按钮(我称之为“addSegue”)，另一个来自表格 View 单元格(称之为“editSegue”)。我还会在列表 Controller 中创建一个属性来保存编辑行的值，或者将其设置为类似 -1 的值以指示它是一个新注释。像这样，

@property (nonatomic) NSInteger editedRow;

- (void) prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender {
    if ([segue.identifier isEqualToString:@"editSegue"]) {
        NMCreateNotesViewController *destination = [segue destinationViewController];
        NSInteger indx = [self.tableView indexPathForCell:(UITableViewCell *)sender].row;
        self.editedRow = index;
        NMNote *note = self.notes[indx];
        destination.note = note;
    }else if ([segue.identifier isEqualToString:@"addSegue"]) {
        self.editedRow = -1;
}

NMCreateNotesViewController 中的 prepareForSegue 方法与您在问题中使用的方法相同。您可以去掉 passedInString 属性，因为我们传递的是整个笔记对象。在列表 Controller 的 unwind 方法中，您可以这样做，

- (IBAction) unwindToList: (UIStoryboardSegue *) segue {

    NMCreateNotesViewController *source = [segue sourceViewController];
    NMNote *note = source.note;

    if (note != nil && self.editedRow == -1) {
        [self.notes addObject:note];
    }else{
        [self.notes replaceObjectAtIndex:self.editedRow withObject:note];
    }
    [self.tableView reloadData];
}