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，因为身份验证正在进行并且我从服务器获得响应。

但是当我提供错误的凭据时，此方法以递归方式调用，因此我无法打破它。

请帮助我，如何打破这种情况，以便我应该能够显示身份验证失败警报消息。

- (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]; 
        }
}