Summary of the method of developing reverse value transmission in iOS

There are many ways to reverse value transmission in iOS. Here are several commonly used methods of value transmission (only post related code):

The first type: proxy value transmission
The second controller:

@protocol WJSecondViewControllerDelegate <NSObject>
- (void)changeText:(NSString*)text;
@end
 @property(nonatomic,assign)id<WJSecondViewControllerDelegate>delegate;

- (IBAction)buttonClick:(UIButton*)sender {
_str = ;
[ changeText:];
[ popViewControllerAnimated:YES];
}

The first controller:

- (IBAction)pushToSecond:(id)sender {
WJSecondViewController *svc = [[WJSecondViewController alloc]initWithNibName:@"WJSecondViewController" bundle:nil];
 = self;
 = ;
[ pushViewController:svc animated:YES];
[svc release];
}
- (void)changeText:(NSString *)text{
 = text;
}

The second type: Notification value transmission
The first controller:

 //Register monitoring notice [[NSNotificationCenter defaultCenter] addObserver:self     selector:@selector(limitDataForModel:) name:@"NOV" object:nil];
- (void)limitDataForModel:(NSNotification *)noti{
 = ;
}

The second controller:

//Send notification [[NSNotificationCenter defaultCenter]   postNotificationName:@"NOV" object:gameArray];

The third type: singleton value transmission
Single is a singleton class and has a property titleName of string type
In the second controller:

- (IBAction)buttonClick:(UIButton*)sender {
Single *single = [Single sharedSingle];
 = ;
[ popViewControllerAnimated:YES];
}

The first controller:

- (void)viewWillAppear:(BOOL)animated{
[super viewWillAppear:animated];
Single *single = [Single sharedSingle];
 = ;
}

The fourth type: block value transmission
The second controller:

@property (nonatomic,copy) void (^changeText_block)(NSString*);
- (IBAction)buttonClick:(UIButton*)sender {
_str = ;
self.changeText_block();
[ popViewControllerAnimated:YES];
}

The first controller:

- (IBAction)pushToSecond:(id)sender {
WJSecondViewController *svc = [[WJSecondViewController alloc]initWithNibName:@"WJSecondViewController" bundle:nil];
 = ;
[svc setChangeText_block:^(NSString *str) {
  > = str;
}]；
[ pushViewController:svc animated:YES];
}

The fifth type: extern value transmission
The second controller:

 extern NSString *btn;
- (IBAction)buttonClick:(UIButton*)sender {
btn = ;
[ popViewControllerAnimated:YES];
}

The first controller:

NSString *btn = nil;
- (void)viewWillAppear:(BOOL)animated{
[super viewWillAppear:animated];
 = btn;
}

Sixth type: KVO value transmission
The first controller:

- (void)viewDidLoad {
[super viewDidLoad];
 _vc =[[SecondViewController alloc]init];
//self listen for textValue property in vc[_vc addObserver:self forKeyPath:@"textValue" options:0 context:nil];  
}

The second controller:

- (IBAction)buttonClicked:(id)sender {
 = ;
[ popViewControllerAnimated:YES];
}

In fact, there are many ways to pass values, such as NSUserDefaults, which first keeps the data local, then reads, or writes to plist and other types of files before reading, etc., etc., so I won't list them all here! These codes have been written for a long time. I sorted them out today and they are still quite messy. Please forgive me if there are any wrong or shortcomings!