iOS 网络请求/数据获取/图片上传及加载/多线程加载图片/数据非空处理

前言

1.网络请求

系统请求的方法

分为get请求和post请求
1.1、get请求系统提供了两种方法，一种是Request方式的，一种是URL方式的。下面先说request方式的

NSString * urlStr = @"http://172.16.101.125:8080/wisdombus-controller/mobile/class/queryBusLineList?corpId=0";
NSURL * url = [NSURL URLWithString:urlStr];
NSURLSession * senssion = [NSURLSession sharedSession];//网络请求管理者
NSMutableURLRequest * request = [NSMutableURLRequest requestWithURL:url];//创建请求对象
//创建网络数据请求任务的对象
NSURLSessionDataTask * task1 = [senssion dataTaskWithRequest:request completionHandler:^(NSData * _Nullable data, NSURLResponse * _Nullable response, NSError * _Nullable error) {
        //由NSData对象获取json字符串
        NSString * string = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
        NSLog(@"%@",string);
        //NSData数据转字典
        NSDictionary * dic = [NSJSONSerialization JSONObjectWithData:data options:0 error:nil];
        NSLog(@"%@",dic);
        //回到主线程
        [self performSelector:@selector(actionWithString:) onThread:[NSThread mainThread] withObject:string waitUntilDone:YES];
    }];
[task1 resume];

get请求url方式

NSString * urlStr = @"http://172.16.101.125:8080/wisdombus-controller/mobile/class/queryBusLineList?corpId=0";
NSURL * url = [NSURL URLWithString:urlStr];
//网络请求管理者
NSURLSession * senssion = [NSURLSession sharedSession];
//创建网络数据请求任务的对象
NSURLSessionDataTask * task2 = [senssion dataTaskWithURL:url completionHandler:^(NSData * _Nullable data, NSURLResponse * _Nullable response, NSError * _Nullable error) {
        //获取json字符串
        NSString * string = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
        NSLog(@"%@",string);
    }];
[task2 resume];

1.2、post请求

NSString * urlStr = @"http://172.16.101.125:8080/wisdombus-controller/mobile/class/queryBusLineList";
NSURL * url = [NSURL URLWithString:urlStr];
NSURLSession * senssion = [NSURLSession sharedSession];//网络请求管理者
NSMutableURLRequest * Postrequest = [NSMutableURLRequest requestWithURL:url];
Postrequest.HTTPMethod = @"POST";
    //设置包体
Postrequest.HTTPBody = [@"username=520it&pwd=520it" dataUsingEncoding:NSUTF8StringEncoding];
    //创建任务
    NSURLSessionDataTask * task = [senssion dataTaskWithRequest:Postrequest completionHandler:^(NSData * _Nullable data, NSURLResponse * _Nullable response, NSError * _Nullable error) {
        NSLog(@"%@",[NSJSONSerialization JSONObjectWithData:data options:0 error:nil]);
        NSString * string = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
        [self performSelector:@selector(actionWithString:) onThread:[NSThread mainThread] withObject:string waitUntilDone:YES];
    }];
[task resume];

第三方网络请求--AFNetWorking

在使用网络请求的控制器中引入头文件

#import 

创建请求管理者，并设置相关属性

//创建请求管理者
AFHTTPSessionManager * sessionManager = [AFHTTPSessionManager manager];
//上传设置
sessionManager.requestSerializer = [AFHTTPRequestSerializer serializer];//普通格式上传
//sessionManager.requestSerializer = [AFJSONRequestSerializer serializer]; // 上传JSON格式
sessionManager.requestSerializer.timeoutInterval = 10.0f;
//返回数据设置
sessionManager.responseSerializer = [AFHTTPResponseSerializer serializer];//自己动手解析
//sessionManager.responseSerializer = [AFJSONResponseSerializer serializer]; // AFN会JSON解析返回的数据
// 个人建议还是自己解析的比较好，有时接口返回的数据不合格会报3840错误，大致是AFN无法解析返回来的数据

sessionManager.responseSerializer.acceptableContentTypes = [NSSet setWithObjects:@"text/plain", @"text/json", @"application/json", @"text/javascript", @"text/html",@"charset=utf-8",  nil];
//创建参数和参数值字典
NSDictionary * dic = @{@"corpId":@"0"};
NSString * urlString = @"http://172.16.101.125:8080/wisdombus-controller/mobile/class/queryBusLineList";

post请求

[sessionManager POST:urlString parameters:dic progress:nil success:^(NSURLSessionDataTask * _Nonnull task, id  _Nullable responseObject) {
        NSLog(@"%@",responseObject);
        self.textView2.text = [NSString stringWithFormat:@"%@",responseObject];
    } failure:^(NSURLSessionDataTask * _Nullable task, NSError * _Nonnull error) {
        NSLog(@"%@",error);
}];

get请求

[sessionManager GET:urlString parameters:dic progress:^(NSProgress * _Nonnull downloadProgress) {
    } success:^(NSURLSessionDataTask * _Nonnull task, id  _Nullable responseObject) {
        NSLog(@"%@",responseObject);
        self.textView2.text = [NSString stringWithFormat:@"%@",responseObject];
    } failure:^(NSURLSessionDataTask * _Nullable task, NSError * _Nonnull error) {
        NSLog(@"%@",error);
}];

注意：系统的网络请求的block中请求改变外部变量需要做特殊处理，但是第三方的不需要

2.获取数据，并处理数据

对于数据的处理主要是两种：
一种是NSData转json字符串

NSString * string = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];

一种是NSData数据转字典

NSDictionary * dic = [NSJSONSerialization JSONObjectWithData:data options:0 error:nil];

3.获取导数据后的非空处理

对于获取到的数据，如果不做非空处理，很容易出现数组越界的情况。所以必须得处理，但是不同的后台开发人员，写的接口字段非空时返回的形式多种多样，所以要综合处理多种情况，才能避免出错。
1、对于数组对象，需要判断元素的个数和数组是否为空

if (self.busLineArr.count == 0||self.busLineArr == nil) {
        [self showErrorMessage:@"暂时不能进行切换"];
        return;
    }

2、对于字符串对象，需要判断nil、NSNull对象、@“”、@“null”,等4种情况

if (([str isKindOfClass:[NSNull class]]||str == nil||[[NSString stringWithFormat:@"%@",str] length] < 1||[[NSString stringWithFormat:@"%@",str] isEqualToString:@"(null)"])) {//字符串对象为空
 
}else{//不为空

}

4.图片的上传

图片上传格式比较固定

NSError *error = nil;
NSURLResponse *response = [NSURLResponse new];
NSString *imageStr = @"http://172.16.101.125:8080/wisdombus-controller/mobile/auth/uploadIMG.do";
NSURL *url = [NSURL URLWithString:imageStr];
NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url];
// 设置请求方法
[request setHTTPMethod:@"POST"];
// 设置请求体
[request setHTTPBody:_imageData];
// 设置请求头的内容的类型
[request setValue:[NSString stringWithFormat:@"cesi%.0f.png",[[NSDate date] timeIntervalSince1970]] forHTTPHeaderField:@"fileName"];//图片文件名字
[request setValue:[NSString stringWithFormat:@"%lu",(unsigned long)_imageData.length] forHTTPHeaderField:@"fileSize"];//大小
[request setValue:[NSString stringWithFormat:@"%@"[[NSUserDefaults standardUserDefaults] objectForKey:@"uuid"]] forHTTPHeaderField:@"userId"];//
[request setValue:[NSString stringWithFormat:@"%d",2] forHTTPHeaderField:@"type"];
NSString *contentType = [NSString stringWithFormat:@"Content-Type multipart/form-data; boundary=%@", kBoundary];
[request setValue:contentType forHTTPHeaderField:@"Content-Type"];
// 发送异步请求
NSData *responseData = [NSURLConnection sendSynchronousRequest:request returningResponse:&response error:&error];
if (!error && responseData) {
  NSDictionary *dic = [NSJSONSerialization JSONObjectWithData:responseData options:NSJSONReadingMutableLeaves error:&error];
     if ([[dic objectForKey:@"result"] isEqualToString:@"true"]) {
        //上传成功
     }else {
         //上传错误
     }
    }else if (error) {
      //操作失败
}

5.图片的下载问题

图片加载影响主线程，所以要放到子线程中这里用GCD加载

dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
dispatch_async(queue, ^{
     NSString * urlStr = @"http://img.taopic.com/uploads/allimg/140326/235113-1403260I05466.jpg";
     UIImage * userImag = [UIImage imageWithData:[NSData dataWithContentsOfURL:[NSURL URLWithString:urlStr]]];
      if (userImag != nil) {//请求成功
           dispatch_async(dispatch_get_main_queue(), ^{//返回主线程
                self.imageView.image = userImag;
           });
      }else{//请求失败，或请求不到图片

      }
});