RWDBCritFuncDef1 Class Reference
[Expressions]

Specialization of the base class RWDBCritFormDefinition used for defining SQL functions taking 1 parameter. More...

#include <rw/db/func.h>

Inheritance diagram for RWDBCritFuncDef1:

List of all members.

Public Member Functions
	RWDBCritFuncDef1 (const RWCString &functionName)
virtual RWDBCriterion	operator() (const RWDBExpr &x1)
Private Member Functions
virtual RWDBCriterion	operator() ()
virtual RWDBCriterion	operator() (const RWDBExpr &, const RWDBExpr &)
virtual RWDBCriterion	operator() (const RWDBExpr &, const RWDBExpr &, const RWDBExpr &)
virtual RWDBCriterion	operator() (const RWDBExpr &, const RWDBExpr &, const RWDBExpr &, const RWDBExpr &)

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Detailed Description

RWDBCritFuncDef1 is a specialization of the base class RWDBCritFormDefinition. This class provides a simplified mechanism for defining SQL functions taking 1 parameter. Unlike the base class, this class does not require positional placeholders in its function definitions. Also, since the number of required parameters is fixed, compile-time checking can be done on the number of parameters actually passed.

Synopsis

 #include <rw/db/func.h>
 
 RWDBCritFuncDef1 myFunc("myFunc");

Related Classes

RWDBExprFuncDef1 provides a parallel mechanism for defining an RWDBExpr, rather than using an RWDBCriterion.

The RWDBCritFormDefinition base class may be used directly to gain additional flexibility.

See RWDBCriterion for details on SQL WHERE clauses in the DB Interface Module.

Examples

Imagine that a database vendor's SQL variant provides the boolean function VALID_NAME(string), which can be used in a WHERE clause. The DB Interface Module has no direct support for this function, yet we would like to use it without losing the benefits of high-level constructs for data manipulation. To do so, we can use a function which we define ourselves:

 RWDBCritFuncDef1 validName("VALID_NAME");
 RWDBTable potentialNames = myDbase.table("potentialNames");
 RWDBColumn name = potentialNames["name"];
 RWDBSelector usableNames = myDbase.selector();
 usableNames << name;
 usableNames.where(validName(name));

Notice that the number of actual parameters passed to validName is checked at compile time. Compare this with the example for RWDBCritFormDefinition.

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Constructor & Destructor Documentation

RWDBCritFuncDef1::RWDBCritFuncDef1

(

const RWCString &

functionName

)

Creates an RWDBCritFuncDef1 for a functional expression that takes 1 parameter. After such an RWDBCritFuncDef1 is instantiated, functionName may be used as though it were a predefined function.

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Member Function Documentation

virtual RWDBCriterion RWDBCritFuncDef1::operator()	(	const RWDBExpr &	,
		const RWDBExpr &	,
		const RWDBExpr &	,
		const RWDBExpr &
	)			[private, virtual]

Not applicable to this class. This class defines SQL functions taking one parameter.

Reimplemented from RWDBCritFormDefinition.

virtual RWDBCriterion RWDBCritFuncDef1::operator()	(	const RWDBExpr &	,
		const RWDBExpr &	,
		const RWDBExpr &
	)			[private, virtual]

Not applicable to this class. This class defines SQL functions taking one parameter.

Reimplemented from RWDBCritFormDefinition.

virtual RWDBCriterion RWDBCritFuncDef1::operator()	(	const RWDBExpr &	,
		const RWDBExpr &
	)			[private, virtual]

Not applicable to this class. This class defines SQL functions taking one parameter.

Reimplemented from RWDBCritFormDefinition.

virtual RWDBCriterion RWDBCritFuncDef1::operator()

(

)

[private, virtual]

Not applicable to this class. This class defines SQL functions taking one parameter.

Reimplemented from RWDBCritFormDefinition.

virtual RWDBCriterion RWDBCritFuncDef1::operator()

(

const RWDBExpr &

x1

)

[virtual]

Returns an RWDBCriterion in the form of a function with 1 parameter whose name is the name that was passed to self's constructor.

Reimplemented from RWDBCritFormDefinition.