UINavigationController中的UIViewController不調用委託方法

Question

在我的Storyboard中，我使用帶導航欄的UINavigationController來呈現視圖控制器。通過點擊我放置在導航欄中的UIBarButtonItem，該視圖控制器ViewController2被推送到堆棧。我在界面生成器中通過將鼠標從欄按鈕拖動到ViewController2場景併爲segue選擇「push」進行連接。要返回到第一個視圖控制器，我有一個IBAction，它調用popViewControllerAnimated方法。我使用委託方法將數據發送回第一個視圖控制器，但ViewController2中的字符串沒有被髮送回ViewController。

如何將使用委託方法將ViewController2中輸入的文本傳遞迴第一個ViewController？

ViewController.h

#import <UIKit/UIKit.h> 
@interface ViewController : UIViewController 
@end 

ViewController.m

#import "ViewController.h" 
#import "ViewController2.h" 

@interface ViewController() <UITableViewDelegate,UITableViewDataSource,Vc2Delegate> 

@property (strong,nonatomic) NSArray *tableArray; 
@property (weak,nonatomic) IBOutlet UITableView *listTableView; 

@end 

@implementation ViewController 

- (void)viewDidLoad { 
    [super viewDidLoad]; 

    [self.listTableView setDelegate:self]; 
    [self.listTableView setDataSource:self]; 

    self.tableArray = @[@"item 1",@"item 2",@"item 3"]; 

    ViewController2 *vc2 = [[ViewController2 alloc] init]; 
    [vc2 setDelegate:self]; 
} 

# pragma mark - TableView 

- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView { 
    return 1; 
} 

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section { 
    return self.tableArray.count; 
} 

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath { 

    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:@"ItemCell" forIndexPath:indexPath]; 
    cell.textLabel.text = [self.tableArray objectAtIndex:indexPath.row]; 

    return cell; 
} 

#pragma mark - Delegate Method 

- (void)returnFromVc2:(NSString *)userString { 
    NSLog(@"delegate text is %@",userString); 
} 

@end 

ViewController2.h

#import <UIKit/UIKit.h> 

@protocol Vc2Delegate <NSObject> 

- (void)returnFromVc2:(NSString *)userString; 

@end 

@interface ViewController2 : UIViewController 

@property (weak,nonatomic) id <Vc2Delegate> delegate; 

@end 

ViewController2.m

#import "ViewController2.h" 

@interface ViewController2() 

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

@end 

@implementation ViewController2 

- (void)viewDidLoad { 
    [super viewDidLoad]; 
    // Do any additional setup after loading the view. 
} 

- (IBAction)toPreviousVC:(id)sender { 
    NSLog(@"user text is: %@",self.textField.text); 

    [self.delegate returnFromVc2:self.textField.text]; 

    [self.navigationController popViewControllerAnimated:YES]; 
} 

@end 

Answer 1

您設置委託給本地變量不會是相同的實例，你推一個。

- (void)viewDidLoad { 
    .... 
    ViewController2 *vc2 = [[ViewController2 alloc] init]; 
    [vc2 setDelegate:self]; 
    .... 
} 

你還應該養成檢查你的代表是否可以回覆發送的消息的習慣。

- (IBAction)toPreviousVC:(id)sender { 
    NSLog(@"user text is: %@",self.textField.text); 

    if ([self.delegate respondsToSelector(@selector(returnFromVc2:))]) { 
     [self.delegate returnFromVc2:self.textField.text]; 
    } 
    [self.navigationController popViewControllerAnimated:YES]; 
}