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
AsJson
Returns object as JSON string
function AsJson: UnicodeString
AsXML
Returns object as XML string
function AsXML: UnicodeString
Clone virtual abstract
Clones current expression
function Clone: TDAWhereExpression
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
Kind
Specified kind of TDAWhereExpression
property Kind: TDAWhereKind read
ParseException protected
Raises EDAWhereParseXmlException.
procedure ParseException(aName: string)
Parameters:
- aName: property name.
ParseExpression (TROJSONObject, string): TDAWhereExpression protected overload
Creates new Where expression from Json object.
function ParseExpression(aItem: TROJSONObject; aName: string): TDAWhereExpression
Parameters:
- aItem: Json object
- aName: Name of property
ParseExpression (IXmlNode, string): TDAWhereExpression protected overload
Creates new Where expression from XML node.
function ParseExpression(xr: IXmlNode; aName: string): TDAWhereExpression
Parameters:
- xr: source node.
- aName: Name of property
ParseExpression (TROJSONObject): TDAWhereExpression overload
Creates new Where expression from Json object.
class function ParseExpression(anItem: TROJSONObject): TDAWhereExpression
Parameters:
- anItem: json object
ParseExpression (IXmlNode): TDAWhereExpression overload
Creates new Where expression from XML node.
class function ParseExpression(xr: IXmlNode): TDAWhereExpression
Parameters:
- xr: given XML node.
ReadFromJson virtual abstract
Reads where expression from the Json.
procedure ReadFromJson(aItem: TROJSONObject)
Parameters:
- aItem: Json object
ReadFromXml virtual abstract
Reads where expression from the XML.
procedure ReadFromXml(xr: IXmlNode)
Parameters:
- xr: source node
RemoveEmptyNodes
Removes empty XML nodes from given node
class procedure RemoveEmptyNodes(aNode: IXMLNode)
Parameters:
- aNode: node
Validate virtual
Validates properties of expression.
procedure Validate
WriteToJson virtual
Writes where expression to the Json object.
procedure WriteToJson(aItem: TROJSONObject)
Parameters:
- aItem: destination object
WriteToXml virtual
Writes where expression to the XML node.
procedure WriteToXml(sw: IXmlNode)
Parameters:
- sw: destination node
Kind
Specified kind of TDAWhereExpression
property Kind: TDAWhereKind read
ParseExpression (TROJSONObject): TDAWhereExpression overload
Creates new Where expression from Json object.
class function ParseExpression(anItem: TROJSONObject): TDAWhereExpression
Parameters:
- anItem: json object
ParseExpression (IXmlNode): TDAWhereExpression overload
Creates new Where expression from XML node.
class function ParseExpression(xr: IXmlNode): TDAWhereExpression
Parameters:
- xr: given XML node.
RemoveEmptyNodes
Removes empty XML nodes from given node
class procedure RemoveEmptyNodes(aNode: IXMLNode)
Parameters:
- aNode: node
AsJson
Returns object as JSON string
function AsJson: UnicodeString
AsXML
Returns object as XML string
function AsXML: UnicodeString
Clone virtual abstract
Clones current expression
function Clone: TDAWhereExpression
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
ParseException protected
Raises EDAWhereParseXmlException.
procedure ParseException(aName: string)
Parameters:
- aName: property name.
ParseExpression (TROJSONObject, string): TDAWhereExpression protected overload
Creates new Where expression from Json object.
function ParseExpression(aItem: TROJSONObject; aName: string): TDAWhereExpression
Parameters:
- aItem: Json object
- aName: Name of property
ParseExpression (IXmlNode, string): TDAWhereExpression protected overload
Creates new Where expression from XML node.
function ParseExpression(xr: IXmlNode; aName: string): TDAWhereExpression
Parameters:
- xr: source node.
- aName: Name of property
ReadFromJson virtual abstract
Reads where expression from the Json.
procedure ReadFromJson(aItem: TROJSONObject)
Parameters:
- aItem: Json object
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
WriteToJson virtual
Writes where expression to the Json object.
procedure WriteToJson(aItem: TROJSONObject)
Parameters:
- aItem: destination object
WriteToXml virtual
Writes where expression to the XML node.
procedure WriteToXml(sw: IXmlNode)
Parameters:
- sw: destination node