iOS Block回调

前言

相信大家都觉得使用block会给开发带来很大的便利,block可以轻松实现控件之间的数据传递,对于代理/通知/block三者之中,我个人也是非常倾向于使用block,但是使用block需要注意内存管理问题,不然很容易造成循环引用,造成内存泄露,对于block的知识请自行百度,我今天给大家演示:**1)**controller之间的block传值,**2)**controller 与 view 之间的block传值;希望此文章会给大家一些启发,由于水平有限,如有错误望指正.废话不多说,直接上代码.

项目目录

场景一 controller之间的block传值

首先创建两个控制器类 ViewController 与 oneViewController,其中ViewController中有一个next按钮,点击会push到oneViewController.
先看oneViewController

////  OneViewController.h//  block////  Created by zzyong on 16/2/27.//  Copyright © 2016年 zzyong. All rights reserved.//#import <UIKit/UIKit.h>typedef NSString* (^OneCallBackBlock)();@interface OneViewController : UIViewController- (instancetype) initCallBack:(OneCallBackBlock)callbackBlock;@end////  OneViewController.m//  block////  Created by zzyong on 16/2/27.//  Copyright © 2016年 zzyong. All rights reserved.//#import "OneViewController.h"#import "TwoView.h"@interface OneViewController ()@property (nonatomic,copy) OneCallBackBlock callbackBlock;@property (weak, nonatomic ) IBOutlet UILabel  *titleView;@end@implementation OneViewController- (void)viewDidLoad {    [super viewDidLoad];    //0.初始化设置    self.title = @"One";    _titleView.textColor = [UIColor blackColor];    _titleView.text = nil;    //1.添加twoView    __weak typeof(self) weafSelf = self;    TwoView *two = [[TwoView alloc] initWithBlock:^() {        // block 实现controller 与 view 之间的数据传递        UIViewController *three = [[UIViewController alloc] init];        three.view.backgroundColor = [UIColor grayColor];        three.title = @"TwoViewControll";        [weafSelf.navigationController pushViewController:three animated:YES];    }];    two.frame = CGRectMake(0, CGRectGetMaxY(_titleView.frame) + 10, self.view.bounds.size.width, 40);    two.backgroundColor = [UIColor whiteColor];    [self.view addSubview:two];    //2.添加rightBarButtonItem    UIBarButtonItem  *rightItem = [[UIBarButtonItem alloc] initWithTitle:@"获取" style:UIBarButtonItemStyleDone target:self action:@selector(getViewControllerTitle)];    self.navigationItem.rightBarButtonItem = rightItem;    //3.如不自动获取ViewController的标题,则3秒后自动获取    [self AutoGetViewControllerTitle];}#pragma mark - 私有方法//类似于AFNetworking- (void) AutoGetViewControllerTitle{    dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(3.0 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{        if (_titleView.text.length) {            return ;        }        _titleView.text =  _callbackBlock();        self.navigationItem.rightBarButtonItem.enabled = NO;        NSLog(@"自动返回ViewControllerTitle");    });}//获取ViewController的标题- (void) getViewControllerTitle{    if (_titleView.text.length) {        return ;    }    _titleView.text =  _callbackBlock();    NSLog(@"%@",_callbackBlock());}- (instancetype)initCallBack:(OneCallBackBlock)callbackBlock{    if (callbackBlock) {        _callbackBlock = callbackBlock;    }    return self;}@end

现在看ViewController的代码

////  ViewController.h//  block////  Created by zzyong on 16/2/27.//  Copyright © 2016年 zzyong. All rights reserved.//#import <UIKit/UIKit.h>@interface ViewController : UIViewController@end////  ViewController.m//  block////  Created by zzyong on 16/2/27.//  Copyright © 2016年 zzyong. All rights reserved.//#import "ViewController.h"#import "OneViewController.h"@interface ViewController ()@end@implementation ViewController- (IBAction)next:(UIBarButtonItem *)sender {    __weak typeof(self) weakSelf = self;    OneViewController *one = [[OneViewController alloc] initCallBack:^NSString *{        return [NSString stringWithFormat:@"返回第一个控制器的标题:%@",weakSelf.title];    }];    [self.navigationController pushViewController:one animated:YES];}- (void)viewDidLoad {    [super viewDidLoad];    self.title = @"VC";}- (void)viewDidAppear:(BOOL)animated{    [super viewDidAppear:animated];    NSLog(@"进入--ViewController");}- (void)dealloc {    NSLog(@"ViewController--dealloc");}@end

控制器之间传值中,我使用一个item主动获取 和 采用延时来自动获取ViewController的标题,OneViewController不依赖ViewController也可以轻松获取其title,具体请看注释.

场景二 controller 与 view 之间的block传值

首先先定义一个TwoView继承与UIView,用于跟控制器之间进行交互,当点击view的按钮时,就会通过block回调给OneViewController,也就是反馈到控制器了,此时OneViewController将会push控制器three,假如读者想传递模型数据给控制器,可以创建带参数的block,,然后在控制器中定义一个模型属性.下面请看TwoView类里面的代码

////  TwoView.h//  block////  Created by zzyong on 16/2/27.//  Copyright © 2016年 zzyong. All rights reserved.//#import <UIKit/UIKit.h>typedef void (^TwoFeedBack)();@interface TwoView : UIView- (instancetype) initWithBlock:(TwoFeedBack)block;@end////  TwoView.m//  block////  Created by zzyong on 16/2/27.//  Copyright © 2016年 zzyong. All rights reserved.//#import "TwoView.h"@interface TwoView ()@property (nonatomic,copy) TwoFeedBack block;@property (nonatomic,weak) UIButton *button;@end@implementation TwoView- (instancetype) initWithBlock:(TwoFeedBack)block{    if (self = [super init]) {        _block = block;        UIButton *button = [UIButton buttonWithType:UIButtonTypeCustom];        [button setTitle:@"跳转到第三个控制器" forState:UIControlStateNormal];        [button addTarget:self action:@selector(feedBack) forControlEvents:UIControlEventTouchUpInside];        [button setBackgroundColor:[UIColor redColor]];        [self addSubview:button];        _button = button;    }    return self;}- (void) feedBack{    if (_block) {        _block();    }}- (void)layoutSubviews{    [super layoutSubviews];    _button.frame = CGRectMake(0, 5, self.bounds.size.width, 30);}- (void)dealloc{    NSLog(@"TwoView--dealloc");}@end