第一次使用markdown，网上看了一些介绍都是不同不痒的，我自己灵机一动，用sublime 为我的代码块加了一个Tab.然后粘贴到这里。里面的代码可以直接复制到你的ViewController.m里面测试。记得添加myWebview和Activity。

//
//  ViewController.m
//  CookieTest
//
//  Created by yiLian on 16/8/13.
//  Copyright © 2016年 yiLian. All rights reserved.
//  这个程序规定：用户登录的时候，服务器传回一个cookie值，下次用户再登录时，只要获取到cookie就不用重新登录。

#import "ViewController.h"

@interface ViewController ()<UIWebViewDelegate>
@property (weak, nonatomic) IBOutlet UIWebView               *myWebview;
//@property (weak, nonatomic) IBOutlet UIActivityIndicatorView *Activity;
@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    [self loadExamplePage];
    //self.Activity.hidesWhenStopped = YES;
}
#pragma mark - 加载数据
- (void)loadExamplePage {
    NSURL *URL              = [NSURL URLWithString:@"http://www.baidu.com"];
    NSURLRequest *request   = [NSURLRequest requestWithURL:URL];
    self.myWebview.delegate = self;
    [self.myWebview loadRequest:request];
}
#pragma mark ---webViewDelegate
- (void)webViewDidStartLoad:(UIWebView *)webView{
    [self setCookie];
   // [self.Activity startAnimating];
}
- (void)webViewDidFinishLoad:(UIWebView *)webView
{
    NSData *cookiesData    = [NSKeyedArchiver archivedDataWithRootObject: [[NSHTTPCookieStorage sharedHTTPCookieStorage] cookies]];
    //存储归档后的cookie
    [[NSUserDefaults standardUserDefaults] setObject: cookiesData forKey: @"cookie"];
    
   // [self.Activity stopAnimating];
}
- (void)webView:(UIWebView *)webView didFailLoadWithError:(nullable NSError *)error
{
   // [self.Activity stopAnimating];
}
#pragma mark - 保持cookie
- (void)setCookie{
    //取出保存的cookie
    NSUserDefaults *userDefaults = [NSUserDefaults standardUserDefaults];
    //对取出的cookie进行反归档处理
    NSArray *cookies = [NSKeyedUnarchiver unarchiveObjectWithData:[userDefaults objectForKey:@"cookie"]];
    if (cookies) {
        NSLog(@"有cookie");
        //设置cookie
        NSHTTPCookieStorage *cookieStorage = [NSHTTPCookieStorage sharedHTTPCookieStorage];
        for (NSHTTPCookie *cookie in cookies) {
            [cookieStorage setCookie:cookie];
            if ([cookie.name isEqualToString:@"ylusername"]) { // 这里服务端规定cookie的名称。
                [[NSUserDefaults standardUserDefaults] setObject: cookie.value forKey: @"userID"];
            }
        }
    }else{
        NSLog(@"无cookie");
    }
}
@end