3.3 Member Function Conventions

The names of the member functions of the DBTools.h++ classes follow certain conventions.

Functions that produce objects are named according to the object that is produced. In the example below, an RWDBDatabase produces an RWDBTable, and the RWDBTable produces an RWDBReader:

RWDBTable myTable = myDatabase.table("myTable");
RWDBReader rdr = myTable.reader();

Functions that provide access to data members (accessors) get their names from the name of the data member, and take no arguments. Functions that set the value of a data member (mutators) also get their name from the data member, but require a single argument:

RWCString tableName = myTable.name();            // accessor
myTable.name("aNewName");                        // mutator

Functions that provide type conversions are called asType(), where Type is the name of the type you are converting to. Here we are converting an RWDBDateTime into an RWCString:

RWDBDateTime now;
cout << now.asString();

Classes that are closely tied to SQL concepts often have member function names that suggest their SQL syntax. For example:

RWDBTable myTable = myDatabase.table("myTable");  //producer
RWDBSelector select = myDatabase.selector();      //producer
select.where(myTable["key"] == 100);   // SQL "WHERE" clause

Finally, we have freely overloaded the extraction, or shift-out operator >>, and the insertion or shift-in operator <<. The insertion operator is used to add elements to objects sequentially; the extraction operator is used to remove elements from objects sequentially. Assume we have a parts table in a database, with columns partID, partName, and supplier, and the following piece of SQL code:

SELECT partID, partName
FROM parts
WHERE supplier = 'Acme Parts'

The following example implements this SQL code fragment in DBTools.h++ code, then prints the results. Notice how the insertion and extraction operators are used on //1 and //2.

RWDBTable parts = myDatabase.table("parts");
RWDBSelector select = myDatabase.selector();

select << parts["partID"] << parts["partName"];                //1
select.where(parts["supplier"] == "Acme Parts");

RWDBReader reader = select.reader();
while(reader()) {
  long partID;
  RWCString partName;
  reader >> partID >> partName;                                //2
  cout << partID << "\t" << partName << endl;
}

The insertion operators on //1 add parts.partID and parts.partName to the select list of the selector. The extraction operators on //2 take results from the reader and assign them to the local variables partID and partName.