关于Block回调的简单应用

在最近的学习中常常会遇到关于Block回调的应用，因此总结一下关于Block回调的基本用法：

一、业务逻辑：在主页面中添加一个搜索视图控件（XBRSearchBar），当开始编辑搜索栏时，经过Block回调跳转至新的页面；

二、Class说明：
a、XBRSearchBar:视图控件，继承UISearchBar；在该类中添加Block属性，系统默认会生成Block属性的set和get方法，在实际使用时，能够根据实际业务逻辑须要重写Block的set和get方法（我这测试的比较简单，就不重写直接使用默认的方法了），而Block的具体实现也不用写，而是放在视图控制器中实现；
b、ViewController:视图控制器，能够根据实际须要添加Block的具体实现；
c、XBRSearchViewController:视图控制器，用于管理跳转后的新视图，与Block的回调不要紧了；

三、相关的测试代码以下：

#import <UIKit/UIKit.h>
@interface XBRSearchBar : UISearchBar <UISearchBarDelegate>
// 添加Block属性（返回值为：void, 不带参数）
@property (nonatomic, copy) void (^searchBarShouldBeginEditingBlock)();
@end

#import "XBRSearchBar.h"
@implementation XBRSearchBar
// UISearchBar的代理方法，当开始编辑搜索栏时会调用该方法
- (BOOL)searchBarShouldBeginEditing:(UISearchBar *)searchBar{
    // 判断当Block属性不为空时，执行当前Block，就是执行“ViewController”中Block的具体实现代码
    if (_searchBarShouldBeginEditingBlock) self.searchBarShouldBeginEditingBlock();
    return YES;
}
@end

#import <UIKit/UIKit.h>
@interface ViewController : UIViewController
@end

#import "ViewController.h"
#import "XBRSearchBar.h"
#import "XBRSearchViewController.h"

@interface ViewController ()
@property (nonatomic, strong) XBRSearchBar *searchBar;
@end

@implementation ViewController
- (void)viewDidLoad {
    [super viewDidLoad];
    self.view.backgroundColor = [UIColor purpleColor];
    
#pragma mark - 设置searchBar视图    
    _searchBar = [[XBRSearchBar alloc]init];
    _searchBar.delegate = _searchBar;
    _searchBar.placeholder = @"搜索栏";
    _searchBar.backgroundColor = [UIColor clearColor];
    _searchBar.showsCancelButton = YES;
    self.navigationItem.titleView = _searchBar;
       
#pragma mark - block回调跳转页面  
    // 弱化self，避免循环引用;
    __weak typeof(self) weakSelf = self;  
    XBRSearchViewController *searchViewController = [[XBRSearchViewController alloc]init];
    // Block的具体实现;
    _searchBar.searchBarShouldBeginEditingBlock = ^{
        [weakSelf.navigationController pushViewController:searchViewController animated:YES];
    };
}
@end

// 如下只是跳转到新页面的一些界面设置，有兴趣能够浏览一下
#import <UIKit/UIKit.h>
@interface XBRSearchViewController : UIViewController
@end

#import "XBRSearchViewController.h"
#import "XBRSearchBar.h"

@interface XBRSearchViewController()
@property (nonatomic, strong) XBRSearchBar *searchBar;
@end

@implementation XBRSearchViewController

- (void) viewDidLoad{
    
    [super viewDidLoad];
    self.view.backgroundColor = [UIColor orangeColor];
    _searchBar = [[XBRSearchBar alloc]init];
    _searchBar.placeholder = @"搜索栏";
    _searchBar.showsCancelButton = YES;    
    self.navigationItem.titleView = _searchBar;
}
@end

四、具体的完整代码可参考:连接描述