TDAWhereExpression
Overview
The base abstract class for classes that represent WHERE expression tree nodes:
- TDABetweenExpression represents expression that checks belonging to a range of values;
- TDABinaryExpression combines two other expressions with a binary operator (such as equality or binary logical operators);
- TDAConstantExpression - the constant values that appear in an expression are represented through objects of this class;
- TDAFieldExpression represents the part of expression containing table field names;
- TDAListExpression is a complex expression, represented by a list of expressions;
- TDAMacroExpression represents a call to a macro function, which will be processed by Macro Processor.
- TDANullExpression represents NULL values used in the expression;
- TDAParameterExpression - the parameters (variables) of an expression are represented through objects of this class;
- TDAUnaryExpression represents expressions, based in the application of a unary operator (like the change of sign or logical negation) to another, inner expression;
This class is used to dynamically build WHERE statements from code (Dynamic Where feature of Data Abstract).
Location
- Unit: uDACore.pas
DoValidate protected
Raised exception if aRaiseException is set
procedure DoValidate(aRaiseException: Boolean; aName: string)
Parameters:
- aRaiseException: specifies should the exception be raised or not.
- aName: Name of property
GetWhereKind protected virtual abstract
function GetWhereKind: TDAWhereKind
Kind
property Kind: TDAWhereKind read
ParseException protected
Raises EDAWhereParseXmlException.
procedure ParseException(aName: string)
Parameters:
- aName: property name.
ParseExpression (IXmlNode, string): TDAWhereExpression protected overload
Calls ParseException if xr is nil, otherwise calls overload ParseException.
function ParseExpression(xr: IXmlNode; aName: string): TDAWhereExpression
Parameters:
- xr: source node.
- aName: Name of property
ParseExpression (IXmlNode): TDAWhereExpression overload
Creates new Where expression from XML node.
class function ParseExpression(xr: IXmlNode): TDAWhereExpression
Parameters:
- xr: given XML node.
ReadFromXml virtual abstract
Reads where expression from the XML.
procedure ReadFromXml(xr: IXmlNode)
Parameters:
- xr: source node
RemoveEmptyNodes
class procedure RemoveEmptyNodes(aNode: IXMLNode)
Parameters:
- aNode:
Validate virtual
Validates properties of expression.
procedure Validate
WriteToXml virtual abstract
Writes where expression to the XML.
procedure WriteToXml(sw: IXmlNode)
Parameters:
- sw: destination node
ParseExpression (IXmlNode): TDAWhereExpression overload
Creates new Where expression from XML node.
class function ParseExpression(xr: IXmlNode): TDAWhereExpression
Parameters:
- xr: given XML node.
RemoveEmptyNodes
class procedure RemoveEmptyNodes(aNode: IXMLNode)
Parameters:
- aNode:
DoValidate protected
Raised exception if aRaiseException is set
procedure DoValidate(aRaiseException: Boolean; aName: string)
Parameters:
- aRaiseException: specifies should the exception be raised or not.
- aName: Name of property
GetWhereKind protected virtual abstract
function GetWhereKind: TDAWhereKind
ParseException protected
Raises EDAWhereParseXmlException.
procedure ParseException(aName: string)
Parameters:
- aName: property name.
ParseExpression (IXmlNode, string): TDAWhereExpression protected overload
Calls ParseException if xr is nil, otherwise calls overload ParseException.
function ParseExpression(xr: IXmlNode; aName: string): TDAWhereExpression
Parameters:
- xr: source node.
- aName: Name of property
ReadFromXml virtual abstract
Reads where expression from the XML.
procedure ReadFromXml(xr: IXmlNode)
Parameters:
- xr: source node
Validate virtual
Validates properties of expression.
procedure Validate
WriteToXml virtual abstract
Writes where expression to the XML.
procedure WriteToXml(sw: IXmlNode)
Parameters:
- sw: destination node