iOS中的网络编程-NSURLConnection（二）

HTTP请求的方案

NSURLConnection：用法简单，（坑比较多）
NSURLSession：功能比NSURLConnection强大，苹果目前比较推荐
CFNetwork ：苹果底层，纯C语言
ASIHTTPRequest：功能强大，已停止更新
AFNetworking：简单易用，三方库中比较主流

NSURLConnection

基本类
- NSURL:请求地址
- NSURLRequest：代表一个请求，它包含（NSURL对象、请求方法、请求头、请求体、请求超时时间…）
- NSMutableURLRequest:是NSURLRequest子类，可修改Request里的信息
- NSURLConnection：负责发送请求，建立客户端和服务器的连接，发送数据并收集来自服务器响应的数据
- 接收大数据一般使用代理方法，小数据使用块方法即可
使用步骤
- 创建一个NSURL对象，设置请求路径
- 传入NSURL创建一个NSURLRequest对象，设置请求头和请求体
- 使用NSURLConnection发送请求
请求方式
- 同步请求(当前线程)
- 异步请求（开启新线程）
同步Get请求

- (IBAction)syncGet:(id)sender {
    NSURL *url = [NSURL URLWithString:@"http://localhost:3000/ping"];
    NSURLRequest *request = [NSURLRequest requestWithURL:url];
    NSURLResponse *response = nil;
    NSData *data = [NSURLConnection sendSynchronousRequest:request returningResponse:&response error:nil];
    NSString *requestInfo  = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
    self.textView.text = requestInfo;
    NSLog(@"syncGetData:%@--%@",requestInfo,[NSThread currentThread]);

}

同步Post请求

- (IBAction)syncPost:(id)sender {
    NSURL *url = [NSURL URLWithString:@"http://localhost:3000/upload"];
    NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url];
    //更改请求方法
    request.HTTPMethod = @"POST";
    //设置超时5s
    request.timeoutInterval = 5;
    request.HTTPBody = [@"ss" dataUsingEncoding:NSUTF8StringEncoding];
    NSURLResponse *response = nil;
    NSData *data = [NSURLConnection sendSynchronousRequest:request returningResponse:&response error:nil];
    NSString *requestInfo = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
    NSLog(@"syncPostData:%@--%@",requestInfo,[NSThread currentThread]);
}

异步Get请求

- (IBAction)asynGet:(id)sender {
    NSURL *url = [NSURL URLWithString:@"http://localhost:3000/ping"];
    NSURLRequest *request = [NSURLRequest requestWithURL:url];
    //queue:可以设置指定的线程，如主线程[NSOperationQueue mainQueue]
    [NSURLConnection sendAsynchronousRequest:request queue:[[NSOperationQueue alloc]init] completionHandler:^(NSURLResponse * response, NSData * _Nullable data, NSError * _Nullable connectionError) {
        NSString *requestInfo = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
        NSLog(@"asynGetData:%@--%@",requestInfo,[NSThread currentThread]);
    }];
}

异步Post请求

NSURL *url = [NSURL URLWithString:@"http://localhost:3000/upload"];
    NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url];
    //更改请求方法
    request.HTTPMethod = @"POST";
    //设置超时5s
    request.timeoutInterval = 5;
    [NSURLConnection sendAsynchronousRequest:request queue:[NSOperationQueue mainQueue] completionHandler:^(NSURLResponse * _Nullable response, NSData * _Nullable data, NSError * _Nullable connectionError) {        
        NSString *requestInfo = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
        NSLog(@"asynPostData:%@--%@",requestInfo,[NSThread currentThread]);
    }];

小文件下载

NSURL *url = [NSURL URLWithString:@"http://localhost:3000/download"];

    //方式一：data直接下载
    NSData *data = [NSData dataWithContentsOfURL:url];
    NSLog(@"\n NSData---%lu",(unsigned long)data.length);
    self.textView.text = [NSString stringWithFormat:@"下载完成:%lu",(unsigned long)data.length];


    //方式二：通过请求下载
    NSURLRequest *request = [NSURLRequest requestWithURL:url];
    [NSURLConnection sendAsynchronousRequest:request queue:[NSOperationQueue mainQueue] completionHandler:^(NSURLResponse * _Nullable response, NSData * _Nullable data, NSError * _Nullable connectionError) {
        NSLog(@"\n NSURLConnection---%lu",(unsigned long)data.length);
        self.textView.text = [NSString stringWithFormat:@"下载完成:%lu",(unsigned long)data.length];

    }];

大文件下载

一般下载方式
1、收到服务器响应后初始化一个要存放data的临时缓存区
2、将不断接收的data存放临时缓存区里
3、接收完毕后将临时缓存里的data放入本地存储文件
4、存储完毕后，将临时缓存区清空
弊端：正整个下载过程中，app内存会不断增长，直到将数据写入才会降下来才会降下来

NSURL *url = [NSURL URLWithString:@"http://localhost:3000/download"];
NSURLRequest *request = [NSURLRequest requestWithURL:url];
[NSURLConnection connectionWithRequest:request delegate:self];

---------

    -(void)connection:(NSURLConnection *)connection didReceiveResponse:(NSHTTPURLResponse *)response{
        //获取文件总长度
        self.contentLength = [response.allHeaderFields[@"Content-Length"] integerValue];
        self.fileData = [NSMutableData data];
    }

    -(void)connection:(NSURLConnection *)connection didReceiveData:(nonnull NSData *)data{
           [self.fileData appendData:data];
           NSLog(@"下载进度--%.2f%%",(1.0 * self.fileData.length / self.contentLength) * 100);
            self.textView.text = [NSString stringWithFormat:@"下载进度--%.2f%%",(1.0 * self.fileData.length / self.contentLength) * 100];
    }

-(void)connectionDidFinishLoading:(NSURLConnection *)connection{
        //将临时缓存去的data写入本地文件
    [self.fileData writeToFile:SaveFile atomically:YES];
    self.fileData = nil;
    NSLog(@"写入完毕--%@",SaveFile);
    self.textView.text = [NSString stringWithFormat:@"%@ \n写入完毕--%@",self.textView.text,SaveFile];
}

优化下载过程
为了避免app内存不断增长，最好处理方法是边下载边存储
1、收到服务器响应后,创建一个本地存储的空文件
2、将不断接收的data存放临时缓存区里
3、接收完毕后将临时缓存里的data放入本地存储
4、存储完毕后，将临时缓存区清空

NSURL *url = [NSURL URLWithString:@"http://localhost:3000/download"];
NSURLRequest *request = [NSURLRequest requestWithURL:url];
[NSURLConnection connectionWithRequest:request delegate:self];

---------
    -(void)connection:(NSURLConnection *)connection didReceiveResponse:(NSHTTPURLResponse *)response{
        //获取文件总长度
        self.contentLength = [response.allHeaderFields[@"Content-Length"] integerValue];
        //新建一个空文件
        [[NSFileManager defaultManager]createFileAtPath:SaveFile contents:nil attributes:nil];
        //接收得到data，直接把data写入创建好的文件
        self.handle = [NSFileHandle fileHandleForWritingAtPath:SaveFile]；
     }

    -(void)connection:(NSURLConnection *)connection didReceiveData:(nonnull NSData *)data{

        //指定每一次data写入位置（是指针指向目前存储数据的最后面，避免上一次收到的data覆盖目前的data）
        [self.handle seekToEndOfFile];
        //写入数据
        [self.handle writeData:data];
        self.currentLength += data.length;
        NSLog(@"下载进度--%.2f%%",(1.0 * self.currentLength / self.contentLength) * 100);
        self.textView.text = [NSString stringWithFormat:@"下载进度--%.2f%%",(1.0 * self.currentLength / self.contentLength) * 100]; 
        }

-(void)connectionDidFinishLoading:(NSURLConnection *)connection{
     //存储完毕
    //关闭handle
    [self.handle closeFile];
    self.textView.text = [NSString stringWithFormat:@"%@ \n写入完毕--%@",self.textView.text,SaveFile];
}

通过stream下载
以数据流的形式进行存储

NSURL *url = [NSURL URLWithString:@"http://localhost:3000/download"];
NSURLRequest *request = [NSURLRequest requestWithURL:url];

[NSURLConnection connectionWithRequest:request delegate:self];
------

-(void)connection:(NSURLConnection *)connection didReceiveResponse:(NSHTTPURLResponse *)response{
        //利用NSOutputStream往path中写data（append为YES，每次写入都是追加到文件尾部）
        self.stream = [[NSOutputStream alloc]initToFileAtPath:SaveFile append:YES];
    //
        [self.stream open];
}

-(void)connection:(NSURLConnection *)connection didReceiveData:(nonnull NSData *)data{
[self.stream write:[data bytes] maxLength:data.length];
}

-(void)connectionDidFinishLoading:(NSURLConnection *)connection{
    //关闭stream
    [self.stream close];
    NSLog(@"写入完毕--%@",SaveFile);
    self.textView.text = [NSString stringWithFormat:@"%@ \n写入完毕--%@",self.textView.text,SaveFile];
}

创建压缩文件
pod SSZipArchive库

NSArray *paths = @[
                   @"/Users/soso/Desktop/OTP2.png",
                   @"/Users/soso/Desktop/OTP1.png"
                   ];
    [SSZipArchive createZipFileAtPath:@"/Users/soso/Desktop/test.zip" withFilesAtPaths:paths];
}

解压文件

     [SSZipArchive unzipFileAtPath:@"/Users/soso/Desktop/test.zip" toDestination:@"/Users/soso/Desktop"];

NSURLConnection与Runloop的关系
虽然发送请求写在主线程里，其实内部在是子线程进行的，但是所以的回调方法都是在主线程返回，如果想让回调方法在子线程中进行，那么通过设置队列的方式去其代理回调在其子线程执行

NSURL *url = [NSURL URLWithString:@"http://localhost:3000/download"];
NSURLRequest *request = [NSURLRequest requestWithURL:url];
NSURLConnection *connection =  [NSURLConnection connectionWithRequest:request delegate:self];    

//决定代理方法在哪个队列执行
[connection setDelegateQueue:[[NSOperationQueue alloc]init]];


-(void)connection:(NSURLConnection *)connection didReceiveResponse:(NSHTTPURLResponse *)response{
}

-(void)connection:(NSURLConnection *)connection didReceiveData:(nonnull NSData *)data{

}

-(void)connectionDidFinishLoading:(NSURLConnection *)connection{

}

如果将其请求放在子线程中调用，会导致一个问题，代理的回调方法将无响应，其内部应该当请求发出去时，代理方法将等待服务器的回调，内部应该有一个runloop一直在监听代理回调，一旦runloop监听到source，就去执行处理，为什么在子线程调用就不好使，是因为子线程中runloop默认是没有启动的，因此需要手动启动runloop

dispatch_async(dispatch_get_global_queue(0, 0), ^{
        NSURL *url = [NSURL URLWithString:@"http://localhost:3000/download"];
        NSURLRequest *request = [NSURLRequest requestWithURL:url];
        [NSURLConnection connectionWithRequest:request delegate:self];

        //启动子线程runloop
        [[NSRunLoop currentRunLoop] run];

});

iOS中的网络编程-NSURLConnection（二）

HTTP请求的方案

NSURLConnection

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