cbe::delegate::QueryDelegate Class Reference

#include <QueryDelegate.h>

Classes
struct	ErrorInfo

Public Types
using	Success = cbe::QueryResult
using	Error = QueryError

Public Member Functions
virtual void	onQuerySuccess (cbe::QueryResult &&queryResult)=0
virtual void	onQueryError (cbe::delegate::QueryError &&error, cbe::util::Context &&context)=0

Detailed Description

Delegate class for the asynchronous version of methods:

• CloudBackend::queryWithPath(), and its overloads
• CloudBackend::query(), and its overloads
• CloudBackend::search(), and its overloads
• Container::queryWithPath()
• Container::query(), and its overloads
• Container::search(), and its overloads

Example

  #include "cbe/delegate/QueryDelegate.h"
  ~~~
  #include <condition_variable>
  #include <mutex>
  ~~~
  class MyQueryDelegate :  public cbe::delegate::QueryDelegate {
    std::mutex              mutex{};
    std::condition_variable conditionVariable{};
    // Indicates operation completed - success or failure
    bool                    called = false;
  public:
    cbe::QueryResult  queryResult{cbe::DefaultCtor{}};
    ErrorInfo         errorInfo{};
  private:
    // Called upon successful query.
    void onQuerySuccess(cbe::QueryResult&& queryResult) final {
      {      
        std::lock_guard<std::mutex> lock{mutex};
        // Change state of queryResult member to indicate success
        this->queryResult = std::move(queryResult); 
        // Indicate operation completed, member queryResult indicates success
        called = true;
        // If delegate is reused, clear possibly error state
        errorInfo = ErrorInfo{};
      }           
      conditionVariable.notify_one();
    } // onQuerySuccess()
 
    // Called upon a failed query() or join() call.
    void onQueryError(cbe::delegate::QueryError&& error,
                      cbe::util::Context&&        context) final {
      {
        std::lock_guard<std::mutex> lock{mutex};
        // Activate errorInfo member to indicate no-success
        errorInfo = ErrorInfo{std::move(context), std::move(error)};
        // Indicate operation completed, member object indicates failure 
        called = true;
        // If delegate is reused, clear possibly success state
        queryResult = QueryResult{cbe::DefaultCtor{}};
      }
      conditionVariable.notify_one();
    } // onQueryError()
  public:
    void waitForRsp() {
      std::unique_lock<std::mutex> lock{mutex};
      conditionVariable.wait(lock, [this] { return called; });
      // Reset called flag, so current delegate instance can be reused
      called = false;
    } // waitForRsp()
  }; // class MyQueryDelegate

Usage of the class above, see Example of asynchronous query

Member Function Documentation

onQueryError()

virtual void cbe::delegate::QueryDelegate::onQueryError ( cbe::delegate::QueryError &&  error, cbe::util::Context &&  context  )

pure virtual

Called upon a failed query() or join() call.

Parameters

error	Error information passed from CloudBackend SDK.
context	Additional context information about the original service call that has failed.

onQuerySuccess()

virtual void cbe::delegate::QueryDelegate::onQuerySuccess ( cbe::QueryResult &&  queryResult )

pure virtual

Called upon successful query.

Parameters

queryResult

Instance of a QueryResult containing the result set.

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The documentation for this class was generated from the following file:

• include/cbe/delegate/QueryDelegate.h