在iOS开发中,delegate与block有着非常重要的作用.他们可以将两个控制器之间建立连接,使控制器可以监听其他控制器的事件.
delegate
代理设计模式:当一个控制器想监听另一个控制器做事情时,可以成为这个控制器的代理.
for example:
下图中,A控制器(ContactViewController)想监听B控制器(AddViewController)输入的内容,然后显示在自身cell中.
设计思路:
1.在B控制器中添加代理协议,指定代理需要实现某些方法.
2.在点击保存按钮时,通知代理做事情.
3.跳转至A控制器.
示意图
在AddViewController.h文件添加以下内容:
#import
//自身类,模型类
@class AddViewController,DLContact;
//定义协议内容
@protocol AddViewControllerDelegate
//可选实现
@optional
- (void)addViewController:(AddViewController *)viewController didClickSaveButton:(DLContact *)contact;
@end
@interface AddViewController : UIViewController
//定义代理属性,使其遵守
@property(nonatomic,weak) id delegate;
@end
AddViewController.m文件
#import "AddViewController.h"
#import "DLContact.h"
@interface AddViewController ()
@property (weak, nonatomic) IBOutlet UITextField *nameField;
@property (weak, nonatomic) IBOutlet UITextField *phoneField;
@property (weak, nonatomic) IBOutlet UIButton *saveBtn;
@end
@implementation AddViewController
- (void)viewDidLoad {
[super viewDidLoad];
//更改navigationItem的文字内容
self.title = @"添加联系人";
//加载完成时获取焦点
[_nameField becomeFirstResponder];
//监听文字内容改变
[_nameField addTarget:self action:@selector(textChange:) forControlEvents:UIControlEventEditingChanged];
[_phoneField addTarget:self action:@selector(textChange:) forControlEvents:UIControlEventEditingChanged];
}
//监听方法实现
- (void)textChange:(UITextField *)textFeild{
self.saveBtn.enabled = _nameField.text.length && _phoneField.text.length;
}
//监听按钮点击事件
- (IBAction)save:(id)sender {
//把文字内容包装为模型
DLContact *c = [DLContact contactWithName:_nameField.text phone:_phoneField.text];
//通知代理做事情
if ([_delegate respondsToSelector:@selector(addViewController: didClickSaveButton:)]) {
[_delegate addViewController:self didClickSaveButton:c];
}
//返回上一个界面
[self.navigationController popViewControllerAnimated:YES];
}
@end
ContactViewController.m文件
#import "ContactViewController.h"
#import "AddViewController.h"
#import "DLContact.h"
@interface ContactViewController ()
//定义可变数组接收模型数据
@property (nonatomic,strong) NSMutableArray *contacts;
@end
@implementation ContactViewController
//懒加载
- (NSMutableArray *)contacts{
if (_contacts == nil) {
_contacts = [NSMutableArray array];
}
return _contacts;
}
- (void)viewDidLoad {
[super viewDidLoad];
//设置tableView有内容时显示分割线
self.tableView.tableFooterView = [[UIView alloc] init];
}
- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender{
//获取AddViewController
AddViewController *vc = segue.destinationViewController;
//设置代理为当前控制器
vc.delegate = self;
}
//遵守,并实现代理方法
- (void)addViewController:(AddViewController *)didClickSaveButtonWithContact :(DLContact *)contact{
//将模型数据添加到数组
[self.contacts addObject:contact];
//刷新tableView
[self.tableView reloadData];
}
#pragma mark - Table view data source
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
//返回cell数
return self.contacts.count;
}
//返回cell的内容
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
static NSString *ID = @"cell";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:ID];
if (cell == nil) {
cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleValue1 reuseIdentifier:ID];
}
//取出模型数据给cell赋值
DLContact *c = self.contacts[indexPath.row];
cell.textLabel.text = c.name;
cell.detailTextLabel.text = c.phone;
return cell;
}
@end
blcok
下面用block来实现上述内容:
AddViewController.h文件
#import
@class AddViewController,DLContact;
//定义block别名
typedef void(^AddViewControllerBlock)(DLContact *);
@interface AddViewController : UIViewController
//定义block属性
@property (nonatomic,strong) AddViewControllerBlock block;
@end
AddViewController.m文件
#import "AddViewController.h"
#import "DLContact.h"
@interface AddViewController ()
@property (weak, nonatomic) IBOutlet UITextField *nameField;
@property (weak, nonatomic) IBOutlet UITextField *phoneField;
@property (weak, nonatomic) IBOutlet UIButton *saveBtn;
@end
@implementation AddViewController
- (void)viewDidLoad {
[super viewDidLoad];
self.title = @"添加联系人";
[_nameField becomeFirstResponder];
[_nameField addTarget:self action:@selector(textChange:) forControlEvents:UIControlEventEditingChanged];
[_phoneField addTarget:self action:@selector(textChange:) forControlEvents:UIControlEventEditingChanged];
}
- (void)textChange:(UITextField *)textFeild{
self.saveBtn.enabled = _nameField.text.length && _phoneField.text.length;
}
- (IBAction)save:(id)sender {
//包装模型
DLContact *c = [DLContact contactWithName:_nameField.text phone:_phoneField.text];
//判断block有值时执行指定代码块
if (_block) {
_block(c);
}
//返回上一个控制器
[self.navigationController popViewControllerAnimated:YES];
}
@end
ContactViewController.m文件
#import "ContactViewController.h"
#import "AddViewController.h"
#import "DLContact.h"
@interface ContactViewController ()
//定义可变数组接收模型数据
@property (nonatomic,strong) NSMutableArray *contacts;
@end
@implementation ContactViewController
//懒加载
- (NSMutableArray *)contacts{
if (_contacts == nil) {
_contacts = [NSMutableArray array];
}
return _contacts;
}
- (void)viewDidLoad {
[super viewDidLoad];
//设置tableView有内容时显示分割线
self.tableView.tableFooterView = [[UIView alloc] init];
}
- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender{
//拿到AddViewController
AddViewController *vc = segue.destinationViewController;
//给block赋值,需要时再执行
vc.block = ^(DLContact *contact){
//将模型添加到数组
[_contacts addObject:contact];
//刷新tableView
[self.tableView reloadData];
};
}
#pragma mark - Table view data source
//返回cell的个数
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
return self.contacts.count;
}
//给cell赋值
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
static NSString *ID = @"cell";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:ID];
if (cell == nil) {
cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleValue1 reuseIdentifier:ID];
}
DLContact *c = self.contacts[indexPath.row];
cell.textLabel.text = c.name;
cell.detailTextLabel.text = c.phone;
return cell;
}
@end
总结:delegate与block都能进行对控制器监听,delegate方式需要定义协议,写方法名.block则相对比较简单,只需定义block属性,在需要使用时赋值指定代码块即可.开发中建议使用block,这也是苹果官方大力推荐的.
Tips:在xocde中,如果想定义block又记不清楚格式,可以输入inline,系统会自动提示block代码块.
快速定义block演示:
快速定义block
项目完成后效果图:
效果图