我做了一个简单的项目来解释我的问题。基本上我所做的是用Master Detail Application的模板进行项目。然后在
没有
-(void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
if([segue.identifier isEqualToString:@"showDetail"])
{
[segue.destinationViewController setCellName2:@"New String"];
}
}
@property(nonatomic,strong) NSString *cellName2;
@synthesize cellName2;
- (void)viewDidLoad
{
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
NSLog(@"%@", cellName2);
}
我的问题出在我设置cellName2的detailViewController中，我无法设置它，因为detailViewController是receivingViewController的{{1}}。他们的方法是设置segView的sendingViewController结束吗？
在Firo回答之后，我的代码现在看起来像这样
MasterViewContoller.h
segue的.m
#import <UIKit/UIKit.h>
#import "DetailViewController.h"
@interface MasterViewController : UITableViewController <DetailViewDelegate>
@property(nonatomic,strong) NSString *cellName2;
@end
DetailViewContoller.h
#import "MasterViewController.h"
#import "DetailViewController.h"
@interface MasterViewController () {
NSMutableArray *_objects;
}
@end
@implementation MasterViewController
@synthesize cellName2;
- (void)awakeFromNib
{
[super awakeFromNib];
}
- (void)viewDidLoad
{
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
self.navigationItem.leftBarButtonItem = self.editButtonItem;
UIBarButtonItem *addButton = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemAdd target:self action:@selector(insertNewObject:)];
self.navigationItem.rightBarButtonItem = addButton;
self.cellName2 = cellName;
NSLog(@"%@", self.cellName2);
}
- (void)didReceiveMemoryWarning
{
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}
- (void)insertNewObject:(id)sender
{
if (!_objects) {
_objects = [[NSMutableArray alloc] init];
}
[_objects insertObject:[NSDate date] atIndex:0];
NSIndexPath *indexPath = [NSIndexPath indexPathForRow:0 inSection:0];
[self.tableView insertRowsAtIndexPaths:@[indexPath] withRowAnimation:UITableViewRowAnimationAutomatic];
}
#pragma mark - Table View
- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
{
return 1;
}
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
return _objects.count;
}
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:@"Cell" forIndexPath:indexPath];
NSDate *object = _objects[indexPath.row];
cell.textLabel.text = [object description];
return cell;
}
- (BOOL)tableView:(UITableView *)tableView canEditRowAtIndexPath:(NSIndexPath *)indexPath
{
// Return NO if you do not want the specified item to be editable.
return YES;
}
- (void)tableView:(UITableView *)tableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath
{
if (editingStyle == UITableViewCellEditingStyleDelete) {
[_objects removeObjectAtIndex:indexPath.row];
[tableView deleteRowsAtIndexPaths:@[indexPath] withRowAnimation:UITableViewRowAnimationFade];
} else if (editingStyle == UITableViewCellEditingStyleInsert) {
// Create a new instance of the appropriate class, insert it into the array, and add a new row to the table view.
}
}
/*
// Override to support rearranging the table view.
- (void)tableView:(UITableView *)tableView moveRowAtIndexPath:(NSIndexPath *)fromIndexPath toIndexPath:(NSIndexPath *)toIndexPath
{
}
*/
/*
// Override to support conditional rearranging of the table view.
- (BOOL)tableView:(UITableView *)tableView canMoveRowAtIndexPath:(NSIndexPath *)indexPath
{
// Return NO if you do not want the item to be re-orderable.
return YES;
}
*/
-(void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender {
if([segue.identifier isEqualToString:@"showDetail"]) {
/* assigning self as delegate, telling the detail view that I implement
* setCellName2:, so it (the detailVC) can call it whenever it wants to.
*/
[segue.destinationViewController setDelegate:self];
}
}
// my implementation of the DetailViewDelegate protocol that I abide to
/* note: #pragma mark is not required, just for comment, documentation
* and find-ability purposes
*/
//#pragma mark - DetailViewDelegate
// note: this is just a property setter so this is not actually needed
//- (void)setCellName2:(NSString *)cellName {
// self.cellName2 = cellName;
// NSLog(@"%@", self.cellName2);
//}
@end
的.m
#import <UIKit/UIKit.h>
/* defining a protocol, whoever is a DetailViewDelegate must implement my
* defined methods
*/
@protocol DetailViewDelegate <NSObject>
- (void)setCellName2:(NSString *)cellName;
@end
@interface DetailViewController : UIViewController
/* storing a delegate property. Whoever sets themselves to my delegate
* must implement my DetailViewDelegate's methods (setCellName2: in this case)
*/
@property (weak, nonatomic) id<DetailViewDelegate> delegate;
@property (strong, nonatomic) id detailItem;
@property (weak, nonatomic) IBOutlet UILabel *detailDescriptionLabel;
@end
现在的问题是，我收到错误“使用未声明的标识符'cellName';你的意思是'cellName2'吗？”
答案 0 :(得分：3)
您正在寻找代表和协议。由于您没有从detailVC转到masterVC，因此无法将此setter放入prepareForSegue。您需要存储对主服务器的引用并对其进行回调。以下是您使用基本示例的方法：
/* defining a protocol, whoever is a DetailViewDelegate must implement my
* defined methods
*/
@protocol DetailViewDelegate <NSObject>
- (void)setCellName2:(NSString *)cellName;
@end
@interface DetailViewController : UIViewController
/* storing a delegate property. Whoever sets themselves to my delegate
* must implement my DetailViewDelegate's methods (setCellName2: in this case)
*/
@property (weak, nonatomic) id<DetailViewDelegate> delegate;
@end
@implementation DetailViewController
// some action or method
- (IBAction)buttonPress:(id)sender {
// look below at Master's prepareForSegue
/* calling the method that my delegate implements, my delegate can be any
* object that implements my protocol (DetailViewDelegate)
*/
[self.delegate setCellName2:@""];
}
@end
#import "DetailViewController.h"
// saying I implement the DetailViewDelegate protocol (and all necessary methods)
@interface MastViewController : UITableViewController <DetailViewDelegate>
@end
@interface MasterViewController ()
@property(strong, nonatomic) NSString *cellName2;
@end
@implementation MasterViewController
-(void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender {
if([segue.identifier isEqualToString:@"showDetail"]) {
/* assigning self as delegate, telling the detail view that I implement
* setCellName2:, so it (the detailVC) can call it whenever it wants to.
*/
[segue.destinationViewController setDelegate:self];
}
}
// my implementation of the DetailViewDelegate protocol that I abide to
/* note: #pragma mark is not required, just for comment, documentation
* and find-ability purposes
*/
#pragma mark - DetailViewDelegate
// note: this is just a property setter so this is not actually needed
- (void)setCellName2:(NSString *)cellName {
_cellName = cellName
NSLog("%@", self.cellName);
}
@end
我会向您提供有关委托和协议的更多信息，但在处理iOS开发时这是一种非常常见的模式。您也应该对代理和协议非常熟悉，您会发现它在许多情况下都很有用，它将帮助您更好地理解iOS开发并使您成为更有能力的程序员。如果某些东西不起作用（或有意义），请告诉我。我只是在SO中打字，所以可能会有一些轻微的错误。
注意：如果这与原始问题相差甚远，您可能需要创建一个新问题。
您的主要问题是self.cellName2 = cellName;中有MasterViewController。根据您的原始帖子，您希望DetailVC设置此权限，对吧？因此，需要进入DetailViewController的{{1}}：
viewDidLoad然后删除：
- (void)viewDidLoad {
[super viewDidLoad];
[self.delegate setCellName2:@"My custom text!"];
}
来自self.cellName2 = cellName;
NSLog(@"%@", self.cellName2);
的{{1}}。你的错误是在那里的第一行（我假设）。什么是MasterViewController？它不是字符串，您没有将其定义为变量或属性，因此错误。
答案 1 :(得分：0)
您确定代码是在正确的类中吗？并且你在故事板中正确连接了segue？
在DetailViewController代码中，指示segue标识符为“showDetail”。在我看来，你应该在你的MasterViewController中处理它，因为模式通常是MasterViewController负责监视DetailViewController以显示细节。
基本上，如果segue的destinationViewController属性不是MasterViewController的实例，那么segue未正确配置或您的代码位于错误的位置。
如果我弄错了，请发布更多代码。