CCacheEntry<T>::ContainsValue

Indicates if the specified entry is in the cache and is valid.

Syntax

bool CCacheEntry<T>::ContainsValue(T value, const CString& strModel);

Parameters

value

[in] Value to check.

strModel

[in] The current instrument model.

Return value

Returns true if the specified value is in the cache and is valid, otherwise false.

Example

The following example demonstrates use of the ContainsValue function.

CoAcme4321.cpp

STDMETHODIMP Acme4321::put_Bandwidth(double Bandwidth)
{
  HRESULT hr = S_OK;

   // Retrieve the cache entry for the Bandwidth property
   CCacheEntry<double>* pEntry = GetOrCreateCacheEntry<double>(_T("IAcme4321.Bandwidth"));

   // If the value is in the cache AND is valid, simply return since we don't need to send the instrument command
   if (pEntry->ContainsValue(Bandwidth, GetModel()))
      return S_OK;

   // If we get this far, then the new value is not in the cache, so we
   // must communicate with the instrument to set the value
   HRESULT hr = io.Printf(_T("SENSE:BAND %.15g"), Bandwidth);

   if (SUCCEEDED(hr))
   {
      // The new value was successfully sent to the instrument, so update the cache
      pEntry->UpdateValue(Bandwidth);
   }

  return hr;
}

See also

• GetOrCreateCacheEntry
• State Caching Overview