URLRequest 的一个实例

URLRequest 的一个实例

//Createtherequest.
//所构建的NSURLRequest具有一个依赖于缓存响应的特定策略，cachePolicy取得策略，timeoutInterval取得超时值
NSURLRequest*theRequest=[NSURLRequestrequestWithURL:[NSURLURLWithString:@"http://www.apple.com/"]
cachePolicy:NSURLRequestUseProtocolCachePolicy
timeoutInterval:60.0];
//createtheconnectionwiththerequest
//andstartloadingthedata
NSURLConnection*theConnection=[[NSURLConnectionalloc]initWithRequest:theRequestdelegate:self];
if(theConnection){
//CreatetheNSMutableDatatoholdthereceiveddata.
//receivedDataisaninstancevariabledeclaredelsewhere.
receivedData=[[NSMutableDatadata]retain];
}else{
//Informtheuserthattheconnectionfailed.
}

from:http://blog.csdn.net/bl1988530/article/details/6590099

其中：

NSURLRequest默认的cache policy是NSURLRequestUseProtocolCachePolicy， 是最能保持一致性的协议。

NSURLRequestReloadIgnoringCacheData忽略缓存直接从原始地址下载

NSURLRequestReturnCacheDataElseLoad只有在cache中不存在data时才从原始地址下载

NSURLRequestReturnCacheDataDontLoad允许app确定是否要返回cache数据，如果使用这种协议当本地不存在response的时候，创建NSURLConnection or NSURLDownload实例时将会马上返回nil；这类似于离线模式，没有建立网络连接；

你只需要实现以下delegate方法来处理数据响应

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

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

- (void)connection:(NSURLConnection*)connection didFailWithError:(NSError*)error

- (void)connectionDidFinishLoading:(NSURLConnection *)connection

NSURLConnect还提供了一个方便的类方法(class method) : sendSynchronousRequest:returningResponse:error:可用来同步地加载一个URL请求

+ (NSData *)sendSynchronousRequest: (NSURLRequest *)request returningResponse: (NSURLResponse **)response error: (NSError **)error

• request 要装载的URL请求. 这个request 对象 作为初始化进程的一部分,被深度复制(deep-copied). 在这个方法返回之后, 再修改request, 将不会影响用在装载的过程中的request
• reponse 输出参数, 由服务器返回的URL响应
• error 输出参数, 如果在处理请求的过程中发生错误,就会使用. 无错误,就为NULL

一个实现异步get请求的例子：

NSString*url=[NSStringstringWithFormat:@"http://localhost/chat/messages.php?past=%ld&t=%ld",
lastId,time(0)];

NSMutableURLRequest*request=[[[NSMutableURLRequestalloc]init]autorelease];
[requestsetURL:[NSURLURLWithString:url]];
[requestsetHTTPMethod:@"GET"];

NSURLConnection*conn=[[NSURLConnectionalloc]initWithRequest:requestdelegate:self];
if(conn)
{
receivedData=[[NSMutableDatadata]retain];
}
else
{
}


-(void)timerCallback{
//[timerrelease];
[selfgetNewMessages];
}

-(void)connection:(NSURLConnection*)connectiondidReceiveResponse:(NSURLResponse*)response
{
[receivedDatasetLength:0];
}

-(void)connection:(NSURLConnection*)connectiondidReceiveData:(NSData*)data
{
[receivedDataappendData:data];
}

-(void)connectionDidFinishLoading:(NSURLConnection*)connection
{
if(chatParser)
[chatParserrelease];

if(messages==nil)
messages=[[NSMutableArrayalloc]init];

chatParser=[[NSXMLParseralloc]initWithData:receivedData];
[chatParsersetDelegate:self];//setthedelegate
[chatParserparse];//startparse

[receivedDatarelease];

[messageListreloadData];

NSInvocation*invocation=[NSInvocationinvocationWithMethodSignature:
[selfmethodSignatureForSelector:@selector(timerCallback)]];
[invocationsetTarget:self];
[invocationsetSelector:@selector(timerCallback)];
//timer=[NSTimerscheduledTimerWithTimeInterval:5.0invocation:invocationrepeats:NO];
[NSTimerscheduledTimerWithTimeInterval:5.0invocation:invocationrepeats:NO];//ifsetyes,thenvery5secondsupdatathetable
}

一个实现同步Get请求的例子：

//初始化请求
NSMutableURLRequest*request=[[NSMutableURLRequestalloc]init];
//设置URL
[requestsetURL:[NSURLURLWithString:urlStr]];
//设置HTTP方法
[requestsetHTTPMethod:@"GET"];
//发送同步请求,这里得returnData就是返回得数据了
NSData*returnData=[NSURLConnectionsendSynchronousRequest:request
returningResponse:nilerror:nil];
//释放对象
[requestrelease];

from:http://blog.csdn.net/bl1988530/article/details/6590099