iOS Block

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//在需要传值的.h文件中声明block属性

#import <UIKit/UIKit.h>

@interface FirstViewController : UIViewController

@property (nonatomic, retain)UIButton *button;

#warning block第一步声明block属性

//类型一定为copy

@property (nonatomic, copy)void(^myBlock)(UIColor *color);

@end

//在需要传值的.m文件中

#import "FirstViewController.h"

@interface FirstViewController ()

@end

@implementation FirstViewController

#warning block第四步属性block内存释放

- (void)dealloc

{

Block_release(_myBlock);

[super dealloc];

}

- (void)viewDidLoad {

[super viewDidLoad];

// Do any additional setup after loading the view.

self.view.backgroundColor = [UIColor yellowColor];

self.button = [UIButton buttonWithType:UIButtonTypeCustom];

self.button.frame = CGRectMake(20, 100, 100, 40);

self.button.backgroundColor = [UIColor greenColor];

[self.button setTitle:@"第一页" forState:UIControlStateNormal];

[self.button addTarget:self action:@selector(buttonAction:) forControlEvents:UIControlEventTouchUpInside];

[self.view addSubview:self.button];

}

- (void)buttonAction:(UIButton *)button

{

[self.navigationController popToRootViewControllerAnimated:YES];

#warning block第二步执行block

self.myBlock([UIColor blackColor]);

}

- (void)didReceiveMemoryWarning {

[super didReceiveMemoryWarning];

// Dispose of any resources that can be recreated.

}

#pragma mark - Navigation

// In a storyboard-based application, you will often want to do a little preparation before navigation

- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender {

// Get the new view controller using [segue destinationViewController].

// Pass the selected object to the new view controller.

}

@end

//在被传值的.h页面自定义一个按钮，点击按钮完成传值

#import <UIKit/UIKit.h>

#import "FirstViewController.h"

@interface RootViewController : UIViewController

@property (nonatomic, retain)UIButton *button;

@end

//在被传值的.m页面

#import "RootViewController.h"

@interface RootViewController ()

@end

@implementation RootViewController

- (void)viewDidLoad {

[super viewDidLoad];

// Do any additional setup after loading the view.

self.view.backgroundColor = [UIColor redColor];

self.button = [UIButton buttonWithType:UIButtonTypeCustom];

self.button.frame = CGRectMake(20, 100, 100, 40);

self.button.backgroundColor = [UIColor greenColor];

[self.button setTitle:@"根" forState:UIControlStateNormal];

[self.button addTarget:self action:@selector(buttonAction:) forControlEvents:UIControlEventTouchUpInside];

[self.view addSubview:self.button];

}

- (void)buttonAction:(UIButton *)button

{

FirstViewController *first = [[FirstViewController alloc]init];

[self.navigationController pushViewController:first animated:YES];

//无参数无返回值

//block修饰外部变量int a;

__block int a = 0;

void(^block1)(void) = ^(void)

{

a++;

NSLog(@"block1 = %d", a);

};

//调用方法

block1();

//有参数,无返回值

void(^block2)(int a, NSString *string) = ^(int a, NSString *string)

{

NSLog(@"string = %@", string);

};

block2(10, @"大水杯");

//无参数,有返回值

NSString *(^block3)(void) = ^(void)

{

return @"登山包";

};

NSLog(@"block3 = %@", block3());

//有参数,有返回值

NSString *(^block4)(int a, NSString *string) = ^(int a, NSString *string)

{

return[string stringByAppendingString:@"大水杯"];

};

NSString *str = block4(11, @"124");

NSLog(@"%@", str);

#pragma mark ---重点1.block内存管理

//当block内部使用外部变量时,系统会将内存移到栈区 Stack:栈区

//系统分配的内存都放在栈区

//自己开辟的内存在堆区

NSLog(@"block1 = %@", block1);

//block默认放在全局区 Global:全局区

NSLog(@"block2 = %@", block2);

#pragma mark---解决循环引用的方法将self定义为block变量

__block RootViewController *rootV = self;

#warning block第三步 block实现

first.myBlock = ^(UIColor *color)

{

// 记住回调回来的参数直接用,他是另一个页面传过来的

#pragma mark ------重要如果在block内部中使用self属性,会将self引用计数加一,导致循环引用,因此不能使用self,而是将self定义为block变量

rootV.view.backgroundColor = color;

};

//当将block设置成copy类型的属性时, block会被放入堆区中,需要自己手动释放内存

//release时 block在堆区

NSLog(@"myBlock = %@", first.myBlock);

}

- (void)didReceiveMemoryWarning {

[super didReceiveMemoryWarning];

// Dispose of any resources that can be recreated.

}

#pragma mark - Navigation

// In a storyboard-based application, you will often want to do a little preparation before navigation

- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender {

// Get the new view controller using [segue destinationViewController].

// Pass the selected object to the new view controller.

}

@end

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