dtl

DynamicIndexedDBView <DynamicView>


Category: containers	Component type: type

Description

The DynamicIndexedDBView container is a refinement of IndexedDBView used for queries where the number and types of the fields in the query is unknown until runtime. DynamicIndexedDBView specializes the IndexedDBView template to use a variant_row object to hold rows from the query. The variant_row object provides a mechanism to hold an arbitrary number of fields with values of arbitrary types. Individual fields within the row are accessed by using methods from the variant_row object.

Refinement of

IndexedDBView.

Associated types

None, except for those defined by IndexedDBView.

Example:

// Using a DynamicIndexedDBView to read, update and insert records in a database.



// Dynamic IndexedDBView example



// ... classes as in IndexedDBView example  ....



void DynamicIndexedViewExample()

{

 DynamicDBView<ParamObjExample> dynamic_view("DB_EXAMPLE",

	 "INT_VALUE, STRING_VALUE, DOUBLE_VALUE, EXAMPLE_LONG,  EXAMPLE_DATE",

	 "WHERE INT_VALUE BETWEEN (?) AND (?) OR "

	  "STRING_VALUE = (?) OR EXAMPLE_DATE <= (?) ORDER BY EXAMPLE_LONG",

	  BPAExampleObj());



 DynamicIndexedDBView< DynamicDBView<ParamObjExample> >  

	 indexed_view(dynamic_view, 

         "UNIQUE PrimaryIndex; STRING_VALUE;"

         "IndexLongDate; EXAMPLE_LONG, EXAMPLE_DATE",

	 BOUND, USE_ALL_FIELDS, cb_ptr_fun(SetParamsExample));



 // Find the item where the STRING_VALUE matches the string  "Foozle"

 DynamicIndexedDBView< DynamicDBView<ParamObjExample> >::iterator idxview_it =  indexed_view.find(string("Foozle"));





 // Update the item with the key of "Foozle", to read  "Fizzle" instead

 if (idxview_it != indexed_view.end()) {

  variant_row replacement;

  replacement = *idxview_it;

  replacement["STRING_VALUE"] =   string("Fizzle");

  indexed_view.replace(idxview_it, replacement);

 }



 // Now find a second set of items using AlternateIndex

 // The STL convention for equal_range is to return a pair  consisting of: 

 // 1. an iterator referring to the beginning of the list of found  items

 // 2. an iterator pointing to the end of the list of found items. 

 // We will remove all items in this range.

 const TIMESTAMP_STRUCT date_criteria = {2000, 1, 1, 0, 0, 0, 0};

 long long_criteria = 33;

 pair<DynamicIndexedDBView<DynamicDBView<ParamObjExample> >::iterator,

	 DynamicIndexedDBView<DynamicDBView<ParamObjExample> >::iterator>

   	 pr = indexed_view.equal_range_AK("IndexLongDate", long_criteria, date_criteria);



 idxview_it = pr.first;



 cout << "*** Size before erase calls: " << indexed_view.size() << " ***" << endl; 



 // Remove all rows that matched the criteria in our equal_range_AK lookup 

 while (idxview_it !="pr.second)" { 

   // as iterator is invalidated upon an erase(), use a temporary iterator 

   // to point to DataObj to erase 

   // increment idxview_it before we erase so it will still be valid 

   // when we erase the DataObj 

   DynamicIndexedDBView< DynamicDBView<ParamObjExample> >::iterator deleteMe = idxview_it; 

   idxview_it++; 

   indexed_view.erase(deleteMe); 

 } 

 cout << "*** Size after erase calls: " << indexed_view.size() << " ***" << endl; 

 

 // Finally, insert a new item into the container 

 pair<DynamicIndexedDBView< DynamicDBView<ParamObjExample> >::iterator, bool> ins_pr; 

 

 variant_row r(indexed_view.GetDataObj()); 

 r["INT_VALUE"]=459; 

 r["STRING_VALUE"]=string("Unique String #1"); 

 r["DOUBLE_VALUE"]=3.5; 

 r["EXAMPLE_LONG"]=1; 

 r["EXAMPLE_DATE"]=date_criteria; 

 ins_pr=indexed_view.insert(r);

 cout << "insertion succeded=" <<  (ins_pr.second == true ? " true": " false") << endl; 

}

Public base classes

IndexedDBView<DynamicView>

Template parameters

Parameter	Description	Default
`DynamicView`	The type of the dynamic SQL view (usually a DynamicDBView instantiation which will be used as the underlying view for the DynamicIndexedDBView).

Notation

`X`	A type that is a model of DynamicIndexedDBView
`a`	Object of type `X`
`t`	Object of type `X::value_type`
`p`, `q`	Object of type `X::iterator`

Expression semantics

Name	Expression	Precondition	Semantics	Postcondition
Main constructor	X a( DynamicDBView<...> &view, const string &IndexNamesAndFields, BoundMode bm = UNBOUND, KeyMode km = USE_AUTO_KEY, SetParamsFn IndexedDBViewParam = DefaultSetParams<ParamObj>()))		This is exactly the same constructor as that used by IndexedDBView. The only difference is that the view passed in must be of type DynamicDBView rather than a regular DBView. See IndexedDBView for details on the constructor. See the Key Mode documentation for more details about the Key Mode setting.	The size of the container is `0. Rows are operated on by obtaining the appropriate iterator from the container.`
Main constructor accepting an arguments object.	X a(Args args)		Same as above based on an arguments object.	Construct as above, based on the arguments in the Args object. See the description of IndexedDBView::Args for more details.

Members

As per IndexedDBView with the following changes.

Member	Where defined	Description
`X a( DynamicDBView<...> &view, const string &IndexNamesAndFields, BoundMode bm = UNBOUND, KeyMode km = USE_AUTO_KEY, SetParamsFn IndexedDBViewParam = DefaultSetParams<ParamObj>())`	DynamicIndexedDBView	Creates an DynamicIndexedDBView.
X a(Args args)	DynamicIndexedDBView	Same as above, but based on an arguments object.
`X &operator=(const X &other)`		Assignment operator.
`void swap(X &other)`		Swap *this with `other`.