[Xcode]If you want to exchange data between classes, AppDelegate is recommended.

2016年2月29日2023年5月28日 2分

Bono.

Exchanging data between classes is surprisingly difficult.
Using AppDelegate is rather sensible and simple to implement. Furthermore, this method is convenient because it can be used even if the classes are not in a parent-child relationship.

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How to exchange data between classes

How to exchange data between classes

Simply put, the AppDelegate class is used as an intermediary to pass data.
Excerpts from important parts only.

First, in AppDelegate, prepare variables for passing on.

AppDelegate

AppDelegate.h

#import <UIKit/UIKit.h>

@interface AppDelegate : UIResponder <UIApplicationDelegate> {
    UIWindow *window;
    NSString *title1;
    NSString *body1;
}

@property (strong, nonatomic) UIWindow *window;
@property (nonatomic, retain) NSString *title1;
@end

AppDelegate.m

#import "AppDelegate.h"
#import "MainViewController.h"
#import "SubViewController.h"

@implementation AppDelegate

@synthesize window;
@synthesize title1;

Next, tweak the class from which data is passed.
Here, the title of the itemViewController is passed when the screen disappears.

Note that the AppDelegate instance is created in a slightly different way.

ItemViewController

ItemViewcontroller.h

#import <UIKit/UIKit.h>

@interface ItemViewController : UIViewController {
}

@end

ItemViewcontroller.m

#import "ItemViewController.h"
#import "AppDelegate.h"

- (void)viewWillDisappear:(BOOL)animated
{
    AppDelegate *delegate = (AppDelegate *)[[UIApplication sharedApplication] delegate];
    [delegate setTitle1:@"test"];
}

Finally, simply write the process at the destination of the data.

MainViewController

MainViewController.h

#import <UIKit/UIKit.h>

@interface MainViewController : UIViewController {
}

@end

MainViewController.m

#import "MainViewController.h"
#import "AppDelegate.h"

- (void)viewDidAppear:(BOOL)animated
{ 
    AppDelegate *delegate = (AppDelegate *)[[UIApplication sharedApplication] delegate]; NSLog(delegate.title1); 
}