iOS5：willSendRequestForAuthenticationChallenge方法正在运行递归

Question

我正在使用以下代码对远程服务器的用户进行身份验证。如果我提供正确的用户名和密码，则没有问题，因为身份验证正在发生，我从服务器获得响应。

但是当我提供错误的凭据时，会以递归方式调用此方法，因此我无法解决此问题。

请帮助我，如何打破这一点，以便我能够显示身份验证失败的警报消息。

- (void)connection:(NSURLConnection *)connection willSendRequestForAuthenticationChallenge:(NSURLAuthenticationChallenge *)challenge
{

    NSURLCredential *credential = [NSURLCredential credentialWithUser:@"username"
                                                             password:@"password"
                                                          persistence:NSURLCredentialPersistenceForSession];
    [[challenge sender] useCredential:credential forAuthenticationChallenge:challenge];    
}

Answer 1

您需要检查错误计数并相应地取消身份验证质询：

if ([challenge previousFailureCount]) {
    [[challenge sender] cancelAuthenticationChallenge:challenge];
} else {
    [[challenge sender] useCredential:credential forAuthenticationChallenge:challenge];
}

Answer 2

试试这个。

- (void)connection:(NSURLConnection *)connection willSendRequestForAuthenticationChallenge:(NSURLAuthenticationChallenge *)challenge
        {

        if ([challenge previousFailureCount] > 0) {
                // do something may be alert message
            } 
        else
        {

            NSURLCredential *credential = [NSURLCredential credentialWithUser:@"username"
                                                                     password:@"password"
                                                                  persistence:NSURLCredentialPersistenceForSession];
            [[challenge sender] useCredential:credential forAuthenticationChallenge:challenge]; 
        }

}