General query component design
Author: nxyc_twz@163.com
In the current MIS system, data maintenance and data query is its two core functions. How to design a universal query component that enables the development of the MIS system with a unified query interface, which is a problem that MIS system developers have been solving. In the development and design of many years of MIS systems, the author has been designed and practiced, and finally designed to complete this relatively complete, universal query component.
The component inherits from the Tcomponet component, which mainly includes a query form and a form that displays a summary summary. The main design idea is to achieve the purpose of the general query by setting the PARAMS (parameter) of the TQuery component. For how to design a custom component, please refer to: Create a custom component
It is now published its design ideas and skills to share with the majority of programming enthusiasts. Define universal query class
Find strings in the specified string
Function WordPos (Const AWORD, Astring: String): Integer;
/ / Find strings in the specified string
Var s: string;
I, P: Integer;
Begin
S: = '' ANSIUPPERCASE (astring) ''; // ignore the case
For i: = 1 to length (s) do if not (s [i] in identifiers) THEN S [i]: = ''; // constant definition
P: = POS ('' AnsiUppercase (AWORD) '', S);
Result: = P;
END;
Define universal query class
Type
TDBFILTERDIALOG = Class (Tcomponent)
Private
FDIALOG: TMYDBFILTERDIALOG; / / Query Form
ForiginalSQL: TSTRINGS; / / The original SQL statement
FMODIFIEDSQL: TSTRINGS; // Modified SQL statement
FDataSet: tQuery; // Dataset
FDEFAULTMATCHPE: TDBFILTERMATCHPE; // Filter type
FOPTIONS: TDBOPTIONS; // Filter options
FCAPTION: STRING; / / Form Title
Ffields: tstringlist; // field list
ForiginalVariables: TList; // Variable list
SQLProp: String; // SQL attribute
Procedure setDataSet (Const value: tQuery); // Setting the data set
Procedure SetOptions (Const Value: TDBOPTION); // Settings Options
Procedure setcaption (const value: string); // Set the title
Procedure setDefaultMatchType (const value: tdbfiltermatchType); // Set the default match type
Procedure setfields; // set field
Procedure setfieldslist (const value: tstringlist); // Set field list
Procedure setoriginalsql (const value: tstrings); // Set SQL
Procedure restoreSQL; // Restore SQL
Procedure saveparamvalues; // Save the parameter value
{Private Declarations}
protected
{Protected Declarations}
Procedure loaded; override; // Load filter dialog
Procedure Notification; Operation: TOPERATION; override; // Transfer Message
Property Originalsql: Tstrings Read fortersql Write SetoriginalSql;
public
{Public declarations}
Constructor Create (Aowner: Tcomponent); OVERRIDE; // Constructor
DESTRUCTOR Destroy; Override; // Destructor
Function Execute: Boolean; // Execute Query
Procedure rebuildsql; // Rebuild SQL statement
Property Modifiedsql: Tstrings Read Fmodifiedsql;
Published
{Published Declarations}
Property Caption: String Read Fcaption Write setCaption; // Set the title
Property DataSet: TQuery Read FDataSet Write SetDataSet; // Setting Data Set
Property DefaultMatchType: TDBFiltermatchType Read FDefaultmatchType Write SetDefaultMatchType
DEFAULT fdmatchstart; // Filter type
Property Options: TDBOPTIONS Read FOPTIONS WRITE SETOPTIONS DEFAULT
[fdshowcasesensitive, fdshownonmatching]; // filter options
Property Fields: Tstringlist Read Ffields Write setfieldslist;
END;
Define the parameter data variable class
TDBVARIABLE = Class // Parameter data variable
public
Variablename: String; // Variable name
VariableValue: variant; // Variable value
Constructor create (name: string; value: variant); // Construct function, set variable name and variable value
END;
Constructor, set variable name and variable value
Constructor tdbvariable.create (Name: string; value: variant);
Begin
// Construct function, set variable name and variable value
Variablename: = name;
VariableValue: = value;
END;
Constant definition
Const
Identifiers = ['a' .. 'Z', 'a' .. 'Z', '0'. '9', '_', '#', '$', '.', '", '@'];
Procedure register; // Registration component
Registration component
PROCEDURE register;
// Register components
Begin
Registercomponents ('My Database Components', [TDBFilterDialog]);
End; {of register}
Filter type
// Filter match type: Fully match, start space match, match, any location match, range match, no match
TDBFILTERMATCHPE = (fdmatchstart, fdmatchstart, fdmatchend,
FDMATCHANY, FDMATCHRANGE, FDMATCHNON; Filter options
// Filter option: Size-write sensitive display case sensitive display mismatch record
TDBOPTION = (FDSHOWCaseSensitive, fdshownonmatch);
TDBOPTIONS = set of tdboption;
Set data set
Procedure tdbfilterdialog.setDataSet (Const value: tQuery);
Begin
// Set the data set
If not (value is tquery) or (value = nil)) then // If you do not specify a data set or the specified data set is not tQuery, an exception is issued.
Raise Exception.create (SDBFilternondBerror);
//otherwise
FDataSet: = Value;
Sqlprop: = 'sql';
IF ([csdesigning, cslineing] * ComponentState) = [] THEN
Begin
SetFields; // Set field
Originalsql: = Tstrings (getordprings (fdataset, sqlprop); //
END;
END;
Setting Options
Procedure TdbfilterDialog.SetOptions (Const Value: TDBOPTION);
Begin
//Setting Options
FOPTIONS: = Value;
END;
Set the title
Procedure tdbfilterdialog.setcaption (const value: String);
Begin
// Set the title
FCAPTION: = VALUE;
FDIALOG.CAPTION: = fcaption;
END;
(Endlessly)
