iOS协议

       iOS中协议虽然OC基础中有讲过，但一直只是表面的认识，今天在做项目时，有了更深入一些的认识。在请求网络数据并解析xml时协议就体现出它的价值了。解析数据后，最后会通过协议进行加载解析后的数据。
下面以例子说明：
示例一、
* 1、声明协议

@protocol updateSearchDataDelegate <NSObject>-(void)loadDataForShow;@end@interface AuctionDetailXmlParser : NSObject <NSXMLParserDelegate, ASIHTTPRequestDelegate>//定义协议@property (weak,nonatomic) id<updateSearchDataDelegate> delegate;........@end

       可以用协议delegate调用loadDataForShow方法。

• 2、当其它类引入协议时，则需要实现协议里面的方法。

@interface AuctionDetailsViewController : UITableViewController <updateSearchDataDelegate>......@end@implementation AuctionDetailsViewController- (void)getAuctionDetails {    auctionDetailXmpParser = [[AuctionDetailXmlParser alloc] init];   //设置代理，只有设置协议才会调用协议中方法    auctionDetailXmpParser.delegate = self;     [auctionDetailXmpParser getAuctionDetails:strXml Action:actionName];  }- (void)loadDataForShow {  ........}@end

示例二、（当请求另一个viewController时，通过协议可不通过new来请求该viewController方法）

#import <UIKit/UIKit.h>#import "RequestVO.h"//协议@protocol sortDataDelegate <NSObject>@required- (void) loadDataShow : (RequestVO *)requestParams;@end@interface SortViewController : UITableViewController@property (weak,nonatomic) id<sortDataDelegate> delegate;@end

////  SortViewController.m//  BookReader////  Created by Dwen on 13-1-29.////#import "SortViewController.h"#import "Utils.h"@interface SortViewController ()@end@implementation SortViewController@synthesize popover,sortArry;@synthesize sortStr;@synthesize specialCode;@synthesize delegate;- (id)initWithStyle:(UITableViewStyle)style{    self = [super initWithStyle:style];    if (self) {         sortArry = [[NSMutableArray alloc] initWithObjects:CLOSE_COST_ASC,CLOSE_COST_DESC,LOT_ASC,LOT_DESC, nil];    }    return self;}#pragma mark - Table view data source- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView{   return 1;}- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section{    return 4;}- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath{    static NSString *CellIdentifier = @"Cell";    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];    if (cell == nil) {        cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier];    }    cell.textLabel.text =@"test";    cell.textLabel.font = [UIFont fontWithName:@"Arial" size:18];    return cell;}#pragma mark - Table view delegate- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath{    RequestVO *requestVO = [[RequestVO alloc] init];    [delegate loadDataShow:requestVO];//****代理方法解决调用Controller问题}@end

#import <UIKit/UIKit.h>@interface CatalogViewController : UIViewController <sortDataDelegate>@end@interface CatalogViewController ()@end@implementation CatalogViewController//排序- (IBAction)sortAction:(id)sender {    sortVC = [[SortViewController alloc] initWithStyle:UITableViewStylePlain];    sortVC.contentSizeForViewInPopover = CGSizeMake(240, 176);    popover = [[UIPopoverController alloc] initWithContentViewController:sortVC];    [popover presentPopoverFromRect:[self.sortBtn bounds] inView:self.sortBtn permittedArrowDirections:UIPopoverArrowDirectionAny animated:YES];    sortVC.delegate = self;//****该delegate一定要设}- (void)loadDataShow:(RequestVO *)requestParams{}@end