1 #import "ViewController.h"
 2
 3 @interface ViewController ()
 4
 5 @end
 6
 7 @implementation ViewController
 8
 9 - (void)viewDidLoad {
10     [super viewDidLoad];
11
12     //定义block 无返回值，无参数
13     void (^nameBlock)() = ^ () {
14         NSLog(@"姓名： Block");
15     };
16
17     //定义block 有返回值，有参数
18     int (^ageBlock)(int) = ^(int age) {
19         NSLog(@"年龄： %d",age);
20         return age + 1;
21     };
22
23     //调用block
24     nameBlock();
25     int age = ageBlock(3);
26     NSLog(@"》》》年龄：%d",age);
27     nameAndAgeBlock(@"SD.Team",2015);
28 }
29
30 void (^nameAndAgeBlock)() = ^(NSString *name,int age) {
31     NSLog(@"姓名：%@,年龄：%d",name,age);
32 };
33
34 - (void)didReceiveMemoryWarning {
35     [super didReceiveMemoryWarning];
36 }
37
38 @end
39
40 Block 定义与使用

1 - (void)viewDidLoad {
2     [super viewDidLoad];
3     int myAge = 25;
4     void (^updateAge)(int) = ^(int age){
5         myAge = myAge + age;
6         NSLog(@"age:%d",myAge);
7     };
8 }

 1 - (void)viewDidLoad {
 2     [super viewDidLoad];
 3     __block int myAge = 25;
 4     void (^updateAge)(int) = ^(int age){
 5         myAge = myAge + age;
 6         NSLog(@"age:%d",myAge);
 7     };
 8
 9     updateAge(3);
10 }

 1 //SettingViewController.h 文件
 2 @interface SettingViewController : UIViewController
 3 @property (nonatomic, copy) void (^updateAgeBlock)(NSString *age);
 4
 5 @end
 6
 7 //SettingViewController.m 文件
 8 - (IBAction)updateAgeBtnClicked:(id)sender {
 9     if (self.updateAgeBlock) {
10         self.updateAgeBlock(self.ageTextField.text);
11     }
12     [self.navigationController popViewControllerAnimated:YES];
13 }

 1 - (IBAction)settingClicked:(id)sender
 2 {
 3     SettingViewController *settingVC = [[SettingViewController alloc] initWithNibName:@"SettingViewController" bundle:nil];
 4     settingVC.updateAgeBlock = ^(NSString *age){
 5         [self updateAgeLabel:age];
 6     };
 7     [self.navigationController pushViewController:settingVC animated:YES];
 8 }
 9
10 - (void)updateAgeLabel:(NSString *)age
11 {
12     self.ageLabel.text = age;
13 }