iOS ViewController之間傳遞數據

翻譯自stackoverflow的問題

前向傳遞數據：

例如你有ViewControllerA和ViewControllerB，從ViewcontrollerA向ViewcontrollerB傳遞一個BOOL變量：

（1）在ViewControllerB.h創建一個屬性

@property (nonatomic, assign) BOOL *isSomethingEnabled;

（2）在ViewcontrollerA中引入頭文件

#import "ViewControllerB.h"

 當點擊didSelectRowAtIndex或者IBAction的時候可以用以下代碼設置ViewControllerB的屬性

ViewControllerB *viewControllerB = [[ViewControllerB alloc] initWithNib:@"ViewControllerB" bundle:nil];
viewControllerB.isSomethingEnabled = YES;
[self pushViewController:viewControllerB animated:YES];

用Segue前向傳遞數據：

用以下方法傳遞數據：

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

（1）在ViewControllerB.h創建一個屬性

@property (nonatomic, assign) BOOL *isSomethingEnabled;

（2）在ViewcontrollerA中引入頭文件

#import "ViewControllerB.h"

（3）建立一個從ViewControllerA到ViewControllerB的segue，不妨取名為showDetailSegue

（4）實現方法：

-(void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender{
    if([segue.identifier isEqualToString:@"showDetailSegue"]){
        ViewControllerB *controller = (ViewControllerB *)segue.destinationViewController;
        controller.isSomethingEnabled = YES;
    }
}

如果你的view是嵌套在navigation controller里

-(void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender{
    if([segue.identifier isEqualToString:@"showDetailSegue"]){
        UINavigationController *navController = (UINavigationController *)segue.destinationViewController;
        ViewControllerB *controller = (ViewControllerB *)navController.topViewController;
        controller.isSomethingEnabled = YES;
    }
}

后向傳遞數據：

ViewControllerA里面點擊某些按鈕，跳轉到ViewControllerB，里面的事件執行完成后，又要跳轉回ViewControllerA，並且把一些數據傳遞回ViewControllerA。這里需要用到代理模式。

（1）在ViewControllerB.h中，#import下，@interface上聲明一個協議

@protocol ViewControllerBDelegate <NSObject>
- (void)addItemViewController:(ViewControllerB *)controller didFinishEnteringItem:(NSString *)item;
@end

（2）在ViewControllerB.h設置一個delegate屬性

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

（3）在ViewControllerB中，當我們退出這個ViewController的時候

NSString *itemToPassBack = @"Pass this value back to ViewControllerA";
[self.delegate addItemViewController:self didFinishEnteringItem:itemToPassBack];

（4）在ViewControllerA.h中，引入頭文件並實現協議

#import "ViewControllerB.h"

@interface ViewControllerA : UIViewController <ViewControllerBDelegate>

（5）在ViewControllerA.m中，

- (void)addItemViewController:(ViewControllerB *)controller didFinishEnteringItem:(NSString *)item
{
    NSLog(@"This was returned from ViewControllerB %@",item);
}

（6）設置代理

ViewControllerB *viewControllerB = [[ViewControllerB alloc] initWithNib:@"ViewControllerB" bundle:nil];
viewControllerB.delegate = self
[[self navigationController] pushViewController:viewControllerB animated:YES];