Block高级用法(传值)

Block传值比较适用于从后一页向前一页传值

先回顾一下block的基本用法:

1. block的一般写法

定义block

void (^block)(int a) = ^(int a) {
    NSLog(@"block执行: %d", a);
};

block的使用(执行bloc中的代码)

block(10);<span style="white-space:pre"></span>// block中a = 10;

2. 含有block类型的参数的方法调用

// 添加一个使用block的方法

- (void)testBlock:(void(^)(int a) )block
{
    block(30);
}

// 使用方法

[self testBlock:block];

3. block类型重定义

// 把void(^)(int a)类型 重定义为BLOCK

typedef void(^BLOCK)(UIColor);

// 使用新定义的BLOCK变量定义

BLOCK b = ^(int a) {
    NSLog(@"----");
};
b(10);

下面开始进行block传值

准备工作: 创建两个视图控制器(本文为MainViewController, SecondView), 添加一个导航控制器

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

@implementation AppDelegate

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
    // Override point for customization after application launch.
    self.window.backgroundColor = [UIColor whiteColor];
    [self.window makeKeyAndVisible];

    MainViewController *mainVC = [[MainViewController alloc] init];
    UINavigationController *naviVC = [[UINavigationController alloc] initWithRootViewController:mainVC];
    [[self window] setRootViewController:naviVC];

    [mainVC release];
    [naviVC release];
    [_window release];
    return YES;
}

- (void)dealloc
{
    [_window release];
    [super dealloc];
}

1. 在第二页上定义一个block属性 一定要用copy特性

#import <UIKit/UIKit.h>

// 重定义一个Block类型
typedef void(^BL)(UIColor *color);

@interface SecondViewController : UIViewController

// 1. 定义一个block属性 一定要使用copy特性
@property (nonatomic, copy) BL block;

@end

2. 在button触发方法中调用block

注意block的释放方法

#import "SecondViewController.h"

@interface SecondViewController ()

@end

@implementation SecondViewController

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

- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view.

    UIButton *button = [UIButton buttonWithType:UIButtonTypeSystem];
    button.frame = CGRectMake(40, 140, 240, 100);
    [button setTitle:@"" forState:UIControlStateNormal];
    [button setBackgroundColor:[UIColor orangeColor]];
    [button addTarget:self action:@selector(buttonClicked:) forControlEvents:UIControlEventTouchUpInside];
    [self.view addSubview:button];

}

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

- (void)buttonClicked:(UIButton *)button
{
    // 2. 调用
    self.block([UIColor redColor]);

    [self.navigationController popViewControllerAnimated:YES];
}

#import "MainViewController.h"
#import "SecondViewController.h"

// 把void(^)(int a)类型 重定义为BLOCK
typedef void(^BLOCK)(UIColor *color);

@interface MainViewController ()

@end

@implementation MainViewController

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

- (void)testBlock:(void(^)(int a) )block
{
    NSLog(@"啦啦啦瓦洛兰");
}

- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view.

    UIButton *button = [UIButton buttonWithType:UIButtonTypeSystem];
    [button setFrame:CGRectMake(40, 140, 240, 100)];
    [button setTitle:@"推出第二页面" forState:UIControlStateNormal];
    [button setBackgroundColor:[UIColor orangeColor]];
    [button addTarget:self action:@selector(buttonClicked:) forControlEvents:UIControlEventTouchUpInside];
    [[self view] addSubview:button];

    void (^block)(int a) = ^(int a) {
        NSLog(@"block 执行: %d", a);
    };
    block(10);
    void (^block1)(int a) = ^(int a) {
        NSLog(@"aa");
    };
    block1 = block;
    block1(15);

    [self testBlock:block];

    BLOCK b = ^(UIColor *color) {
        NSLog(@"ad");
    };
    b([UIColor redColor]);

}

- (void)buttonClicked:(UIButton *)button
{
    BLOCK b = ^(UIColor *color) {
        [[self view] setBackgroundColor:color];
    };
    SecondViewController *secondVC = [[SecondViewController alloc] init];
    [secondVC setBlock:b];

    [[self navigationController] pushViewController:secondVC animated:YES];
    [secondVC release];
}