正确访问segue的目标视图控制器以分配协议代理

Question

我在实现选择列表时遇到了集成segue和协议的一些问题.

在我的选择列表中.h我有:

#import <UIKit/UIKit.h>

@protocol SelectionListViewControllerDelegate <NSObject>
@required
- (void)rowChosen:(NSInteger)row;
@end

@interface SelectColor : UITableViewController <NSFetchedResultsControllerDelegate>
-(IBAction)saveSelectedColor;
@property (nonatomic, strong) id <SelectionListViewControllerDelegate> delegate;
@end

在我的选择列表中.我有:

@implementation SelectColori
@synthesize delegate;

//this method is called from a button on ui
-(IBAction)saveSelectedColore
{
    [self.delegate rowChosen:[lastIndexPath row]];
    [self.navigationController popViewControllerAnimated:YES];
}

我想通过从另一个表视图执行segue来访问此选择列表视图:

@implementation TableList
...
- (void)selectNewColor
{
    SelectColor *selectController = [[SelectColor alloc] init];
    selectController.delegate = (id)self;
    [self.navigationController pushViewController:selectController animated:YES];

    //execute segue programmatically
    //[self performSegueWithIdentifier: @"SelectColorSegue" sender: self];
}

- (void)rowChosen:(NSInteger)row
{
    UIAlertView * errorAlert = [[UIAlertView alloc] initWithTitle:@"Error Title" message:@"Error Text" delegate:self cancelButtonTitle:@"OK" otherButtonTitles:nil];
    [errorAlert show];
}

如果我使用以下方法导航到选择列表:

[self.navigationController pushViewController:selectController animated:YES];

显示警报.如果我改为使用:

[self performSegueWithIdentifier:@"SelectColorSegue"sender:self];

没有显示警报,因为,我认为,我没有将selectController传递给目标选择列表.有什么想法可以解决这个问题吗？

Answer 1

使用Segue将数据传递给destinationViewController时,您需要使用该方法

- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender {
    if ([segue.identifier isEqualToString:@"SelectColorSegue"]) {
        SelectColor *vc = segue.destinationViewController;
        vc.delegate = self;
    }
}

来自Apple Docs

此方法的默认实现不执行任何操作.子类可以覆盖它并使用它将任何相关数据传递给即将显示的视图控制器.segue对象包含指向其他信息的两个视图控制器的指针.