Overview

使用类似栅栏的机制，更新秘钥。可以是临时密钥，也可以是永久密钥。在没有合法密钥的时候，所有的请求会阻塞在队列里面。直到获取到一个合法密钥，或者获取出错。

示例

@code

 - (void) fenceQueue:(QCloudCredentailFenceQueue *)queue requestCreatorWithContinue:(QCloudCredentailFenceQueueContinue)continueBlock
 {
    QCloudCredential* credential = [QCloudCredential new];
    credential.secretID = @"secretID";
    credential.secretKey = @"secretKey";
     //签名过期时间
    credential.experationDate = [NSDate dateWithTimeIntervalSince1970:1504183628];
    credential.token = @"token";
    QCloudAuthentationV5Creator* creator = [[QCloudAuthentationV5Creator alloc] initWithCredential:credential];
    continueBlock(creator, nil);
 }