IOS網路程式設計 HTTP
阿新 • • 發佈：2018-12-22
HTTP定義了一種在伺服器和客戶端之間傳遞資料的途徑。
URL定義了一種唯一標示資源在網路中位置的途徑。
REQUESTS 和 RESPONSES：
客戶端先建立一個TCP連線，然後傳送一個請求。伺服器受到請求處理後傳送一個響應向客戶端傳遞資料。然後客戶端可以繼續傳送請求或者關閉這個TCP連線。
HTTPS：
在TCP連線建立後，傳送請求之前，需要建立一個一個SSL會話。
request方法和它們的用途
注意：想server傳送大量資料需要用POST，因為GET僅支援傳送少量資料（8KB）。
iOS的NSURLRequest和它的子類NSMutableURLRequest提供了建立HTTP請求的方法。
NSURLResponse 和 它的子類NSHTTPURLResponse 處理返回的資料。
URL：
Protocol包括HTTP、FTP和file。
URL編碼：
NSString *urlString = @"http://myhost.com?query=This is a question";
NSString *encoded = [urlString stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding];
NSURL用來管理URL。
IOS HTTP APIS：
涉及到下面一些類：
NSURL, NSURLRequest, NSURLConnection, 和 NSURLResponse.
1、NSURL
NSURL可以定義本地檔案和網路檔案
NSURL *url = [NSURL urlWithString:@"http://www.google.com"];
NSData *data = [NSData dataWithContentsOfURL:url];
NSURL定義了很多訪問器：
if (url.port == nil) {
NSLog(@"Port is nil");} else { NSLog(@"Port is not nil");}
2、NSURLRequest
建立了NSURL後，就可以用NSURLRequest建立請求了：
NSURL *url = [NSURL URLWithString: @"https://gdata.youtube.com/feeds/api/standardfeeds/top_rated"];if (url == nil) { NSLog(@"Invalid URL");
return;}NSURLRequest *request = [NSURLRequest requestWithURL:url];
if (request == nil) { NSLog(@"Invalid Request"); return; }
NSMutableURLRequest是NSURLRequest 的子類，提供了改變請求的屬性的方法：
NSURL *url = [NSURL urlWithString@"http://server.com/postme"];
NSMutableURLRequest *req = [NSMutableURLRequest requestWithURL:url];
[req setHTTPMethod:@"POST"];[req setHTTPBody:[@"Post body" dataUsingEncoding:NSUTF8StringEncoding]];
如果你要傳送一個圖片或者視訊，那麼用需要用NSInputStream，它沒有把資料全部加在到記憶體。
NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url];NSInputStream *inStream = [NSInputStream inputStreamWithFileAtPath:srcFilePath];[request setHTTPBodyStream:inStream];[request setHTTPMethod:@"POST"];
3、NSURLResponse
4、NSURLConnection
提供了初始化、開始、和取消一個連線。
傳送同步請求：
- (NSArray *) doSyncRequest:(NSString *)urlString { // make the NSURL object from the string NSURL *url = [NSURL URLWithString:urlString]; // Create the request object with a 30 second timeout and a cache policy to always retrieve the // feed regardless of cachability. NSURLRequest *request = [NSURLRequest requestWithURL:url cachePolicy:NSURLRequestReloadIgnoringLocalAndRemoteCacheData timeoutInterval:30.0]; // Send the request and wait for a response NSHTTPURLResponse *response; NSError *error; NSData *data = [NSURLConnection sendSynchronousRequest:request returningResponse:&response error:&error]; // check for an error if (error != nil) { NSLog(@"Error on load = %@", [error localizedDescription]); return nil; } // check the HTTP status if ([response isKindOfClass:[NSHTTPURLResponse class]]) { NSHTTPURLResponse *httpResponse = (NSHTTPURLResponse *)response; if (httpResponse.statusCode != 200) { return nil; } NSLog(@"Headers: %@", [httpResponse allHeaderFields]); } // Parse the data returned into an NSDictionary NSDictionary *dictionary = [XMLReader dictionaryForXMLData:data error:&error]; // Dump the dictionary to the log file NSLog(@"feed = %@", dictionary); NSArray *entries =[self getEntriesArray:dictionary]; // return the list if items from the feed. return entries;}
Queued Asynchronous Requests：
- (void) doQueuedRequest:(NSString *)urlString delegate:(id)delegate { // make the NSURL object NSURL *url = [NSURL URLWithString:urlString]; // create the request object with a no cache policy and a 30 second timeout. NSURLRequest *request = [NSURLRequest requestWithURL:url cachePolicy:NSURLRequestReloadIgnoringLocalAndRemoteCacheData timeoutInterval:30.0]; // If the queue doesn't exist, create one. if (queue == nil) { queue = [[NSOperationQueue alloc] init]; } // send the request and specify the code to execute when the request completes or fails. [NSURLConnection sendAsynchronousRequest:request queue:queue completionHandler:^(NSURLResponse *response, NSData *data, NSError *error) { if (error != nil) { NSLog(@"Error on load = %@", [error localizedDescription]); } else { // check the HTTP status if ([response isKindOfClass:[NSHTTPURLResponse class]]) { NSHTTPURLResponse *httpResponse = (NSHTTPURLResponse *)response; if (httpResponse.statusCode != 200) { return; } NSLog(@"Headers: %@", [httpResponse allHeaderFields]); } // parse the results and make a dictionary NSDictionary *dictionary = [XMLReader dictionaryForXMLData:data error:&error]; NSLog(@"feed = %@", dictionary); // get the dictionary entries. NSArray *entries =[self getEntriesArray:dictionary]; // call the delegate if ([delegate respondsToSelector:@selector(setVideos:)]) { [delegate performSelectorOnMainThread:@selector(setVideos:) withObject:entries waitUntilDone:YES]; } } }];}
NSURLConnection start方法和Delegate：
GET：
NSURL *url=[[ NSURL alloc ] initWithString :urlString]; NSMutableURLRequest *request=[[NSMutableURLRequest alloc ] init ]; NSURLConnection *connection = [[ NSURLConnection alloc ] initWithRequest :request delegate : self ]; if (connection) { [connection start]; } else { NSLog ( @"sorry" ); }/** NSURLConnectionDataDelegate*/- (void)connection:(NSURLConnection*)connection didReceiveResponse:(NSURLResponse *)response{
[activityIndicator startAnimating]; //UIActivityIndicatorView NSLog(@"Did Receive Response %@", response); responseData = [[NSMutableData alloc]init];}- (void)connection:(NSURLConnection*)connection didReceiveData:(NSData*)data{ //NSLog(@"Did Receive Data %@", data); [responseData appendData:data]; //NSMutableData}- (void)connection:(NSURLConnection*)connection didFailWithError:(NSError*)error{ NSLog(@"Did Fail");}- (void)connectionDidFinishLoading:(NSURLConnection *)connection{
[activityIndicator stopAnimating];
NSLog(@"Did Finish"); // Do something with responseData}
POST：
//initialize new mutable data NSMutableData *data = [[NSMutableData alloc] init]; self.receivedData = data; //initialize url that is going to be fetched. NSURL *url = [NSURL URLWithString:@"http://www.snee.com/xml/crud/posttest.cgi"]; //initialize a request from url NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:[url standardizedURL]]; //set http method [request setHTTPMethod:@"POST"]; //initialize a post data NSString *postData = [[NSString alloc] initWithString:@"fname=example&lname=example"]; //set request content type we MUST set this value. [request setValue:@"application/x-www-form-urlencoded; charset=utf-8" forHTTPHeaderField:@"Content-Type"]; //set post data of request [request setHTTPBody:[postData dataUsingEncoding:NSUTF8StringEncoding]]; //initialize a connection from request NSURLConnection *connection = [[NSURLConnection alloc] initWithRequest:request delegate:self]; self.connection = connection; //start the connection [connection start];
非同步請求：
非同步請求需要一個run loop來操作代理物件，GCD和NSOperationQueue預設並沒有run loop，所以如果你想在後臺發起一個HTTP請求，必須確保有run loop。
NSURLConnection connection = [[NSURLConnection alloc] initWithRequest:requestdelegate:self startImmediately:NO];[connection scheduleInRunLoop:[NSRunLoop mainRunLoop] forMode:NSDefaultRunLoopMode];[connection start];
上面的程式碼是在主執行緒執行，如果想在其他執行緒執行，可以在其他執行緒新建一個run loop，並繫結到connection。