iOS中使用block传值

#import <UIKit/UIKit.h>

@interface MainView : UIViewController
{
IBOutlet UIButton* btn;
IBOutlet UILabel* labShow;
}
-(IBAction)push:(id)sender;
@end

#import "MainView.h"
#import "SecondView.h"

@implementation MainView

- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
if (self) {
}
return self;
}

- (void)didReceiveMemoryWarning
{
[super didReceiveMemoryWarning];
}

#pragma mark - View lifecycle

- (void)viewDidLoad
{
[super viewDidLoad];
}
-(IBAction)push:(id)sender
{
SecondView *s = [[SecondView alloc] initwithBlock:^(NSString *str){
NSLog(@"%@",str);
labShow.text = str;
}];
[self.navigationController pushViewController:s  animated:YES];
[s release];
}
- (void)viewDidUnload
{
[super viewDidUnload];
}

- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation
{
return (interfaceOrientation == UIInterfaceOrientationPortrait);
}

@end

SecondView.h

#import <UIKit/UIKit.h>
typedef void (^MyBlock)(NSString *);

@interface SecondView : UIViewController
{
IBOutlet UITextField* txtView;
MyBlock my;
}
-(IBAction)back:(id)sender;
-(id)initwithBlock:(MyBlock)str;
@end

SecondView.m

#import "SecondView.h"

@implementation SecondView

-(id)initwithBlock:(MyBlock)str
{
self = [super init];
if(self)
{
my = str;
}
return self;
}
-(IBAction)back:(id)sender
{
NSString* s = txtView.text;
if(my)
{
my(s);
}
[self.navigationController popViewControllerAnimated:YES];
}

- (void)didReceiveMemoryWarning
{
[super didReceiveMemoryWarning];
}
-(void)dealloc{
Block_release(my);
[super dealloc];

}
#pragma mark - View lifecycle

- (void)viewDidLoad
{
[super viewDidLoad];
}

- (void)viewDidUnload
{
[super viewDidUnload];
}

- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation
{
return (interfaceOrientation == UIInterfaceOrientationPortrait);
}

@end