我正在尝试使用以下代码将iOS端点订阅到SNS主题:letsns=AWSSNS.defaultSNS()letrequest=AWSSNSCreatePlatformEndpointInput()request.token=deviceTokenStringrequest.platformApplicationArn=SNSPlatformApplicationArnsns.createPlatformEndpoint(request).continueWithExecutor(AWSExecutor.mainThreadExecutor(),withBlock:{(task:AWST