NSURLRequest : 发布数据并读取发布的页面

Question

在 iOS（当前目标 5.0，Base SDK 5.1）中，如何向服务器发送发布请求，然后读取页面内容。例如，页面采用用户名和密码，然后回显 true 或 false。这只是为了更好地理解 NSURLRequest。

提前致谢！

Answer 1

先做几件事

• 决定如何对数据进行编码 - JSON 或 url 编码是一个好的开始。
• 确定返回值 - 它是 1、TRUE 还是 0、FALSE，甚至是 YES/非零空/零。
• 阅读URL Loading System，这是你的朋友。

旨在使您的所有 url 连接异步，以便您的 UI 保持响应。您可以使用 NSURLConnectionDelegate 回调来做到这一点。 NSURLConnection 有个小缺点：你的代码必须解耦。您希望在委托函数中可用的任何变量都需要保存到 ivars 或您请求的 userInfo 字典中。

您也可以使用 GCD，它与 __block 限定符结合使用时，允许您在声明它的位置指定错误/返回代码 - 对于一次性提取很有用。

事不宜迟，这是一个快速而肮脏的 url-encoder：

- (NSData*)encodeDictionary:(NSDictionary*)dictionary {
      NSMutableArray *parts = [[NSMutableArray alloc] init];
      for (NSString *key in dictionary) {
        NSString *encodedValue = [[dictionary objectForKey:key] stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding];
        NSString *encodedKey = [key stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding]; 
        NSString *part = [NSString stringWithFormat: @"%@=%@", encodedKey, encodedValue];
        [parts addObject:part];
      }
      NSString *encodedDictionary = [parts componentsJoinedByString:@"&"];
      return [encodedDictionary dataUsingEncoding:NSUTF8StringEncoding];
    }

使用像 JSONKit 这样的 JSON 库可以让编码变得更容易，考虑一下！

方法 1 - NSURLConnectionDelegate 异步回调：

// .h
@interface ViewController : UIViewController<NSURLConnectionDelegate>
@end

// .m
@interface ViewController () {
  NSMutableData *receivedData_;
}
@end

...

- (IBAction)asyncButtonPushed:(id)sender {
  NSURL *url = [NSURL URLWithString:@"http://localhost/"];
  NSDictionary *postDict = [NSDictionary dictionaryWithObjectsAndKeys:@"user", @"username", 
                            @"password", @"password", nil];
  NSData *postData = [self encodeDictionary:postDict];

  // Create the request
  NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url];
  [request setHTTPMethod:@"POST"];
  [request setValue:[NSString stringWithFormat:@"%d", postData.length] forHTTPHeaderField:@"Content-Length"];
  [request setValue:@"application/x-www-form-urlencoded charset=utf-8" forHTTPHeaderField:@"Content-Type"];
  [request setHTTPBody:postData];

  NSURLConnection *connection = [[NSURLConnection alloc] initWithRequest:request 
                                                                delegate:self];

  [connection start];  
}

- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response {
  [receivedData_ setLength:0];
}

- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data { 
  [receivedData_ appendData:data];
}

- (void)connectionDidFinishLoading:(NSURLConnection *)connection {
  NSLog(@"Succeeded! Received %d bytes of data", [receivedData_ length]);
  NSString *responeString = [[NSString alloc] initWithData:receivedData_
                                                  encoding:NSUTF8StringEncoding];
  // Assume lowercase 
  if ([responeString isEqualToString:@"true"]) {
    // Deal with true
    return;
  }    
  // Deal with an error
}

方法 2 - Grand Central Dispatch 异步函数：

// .m
- (IBAction)dispatchButtonPushed:(id)sender {

  NSURL *url = [NSURL URLWithString:@"http://www.apple.com/"];
  NSDictionary *postDict = [NSDictionary dictionaryWithObjectsAndKeys:@"user", @"username", 
                            @"password", @"password", nil];
  NSData *postData = [self encodeDictionary:postDict];

  // Create the request
  NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url];
  [request setHTTPMethod:@"POST"];
  [request setValue:[NSString stringWithFormat:@"%d", postData.length] forHTTPHeaderField:@"Content-Length"];
  [request setValue:@"application/x-www-form-urlencoded charset=utf-8" forHTTPHeaderField:@"Content-Type"];
  [request setHTTPBody:postData];

  dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
    // Peform the request
    NSURLResponse *response;
    NSError *error = nil;
    NSData *receivedData = [NSURLConnection sendSynchronousRequest:request  
                                           returningResponse:&response
                                                       error:&error];    
    if (error) {
      // Deal with your error
      if ([response isKindOfClass:[NSHTTPURLResponse class]]) {
        NSHTTPURLResponse *httpResponse = (NSHTTPURLResponse*)response;
        NSLog(@"HTTP Error: %d %@", httpResponse.statusCode, error);
        return;
      }
      NSLog(@"Error %@", error);
      return;
    }

    NSString *responeString = [[NSString alloc] initWithData:receivedData
                                                    encoding:NSUTF8StringEncoding];
    // Assume lowercase 
    if ([responeString isEqualToString:@"true"]) {
      // Deal with true
      return;
    }    
    // Deal with an error

    // When dealing with UI updates, they must be run on the main queue, ie:
    //      dispatch_async(dispatch_get_main_queue(), ^(void){
    //      
    //      });
  }); 
}

方法 3 - 使用 NSURLConnection 便利函数

+ (void)sendAsynchronousRequest:(NSURLRequest *)request queue:(NSOperationQueue *)queue completionHandler:(void (^)(NSURLResponse*, NSData*, NSError*))handler

希望这会有所帮助。

Answer 2

  NSData *postData = [someStringToPost dataUsingEncoding:NSUTF8StringEncoding];

  NSURL *url = [NSURL URLWithString:someURLString];
  NSMutableURLRequest *req = [NSMutableURLRequest requestWithURL:url];
  [req setHTTPMethod:@"POST"];
  [req setValue:[NSString stringWithFormat:@"%d", postData.length] forHTTPHeaderField:@"Content-Length"];
  [req setValue:@"application/x-www-form-urlencoded charset=utf-8" forHTTPHeaderField:@"Content-Type"];
  [req setHTTPBody:postData];

  NSError *err = nil;
  NSHTTPURLResponse *res = nil;
  NSData *retData = [NSURLConnection sendSynchronousRequest:req returningResponse:&res error:&err];
  if (err)
  {
    //handle error
  }
  else
  {
    //handle response and returning data
  }

Answer 3

这个项目可能对您的目的非常方便。它将处理您的下载并将其存储在本地。查看链接https://github.com/amitgowda/AGInternetHandler