Overview

NoteCome

Contact : mailto:peter.notenbaert@skynet.be

Contents

Overview

Overview

GenValidator is a COM Component that implements a rule based validator. It allows you to execute generic validations against your data. Through a few simple methods you are able to check whether complex rules evaluate to True or False.

GenValidator is the ideal component to use for validating all records in a database table against rules specified in a rules table. You can add, remove or edit business rules without the need of recompiling your code.

GenValidator is very fast, very easy and very cheap. Your are going to use GenValidator in all your applications once you’ve discovered its power and ease.

Requirements

Microsoft ActiveX Data Objects 2.0. Download from http://www.microsoft.com/data/mdac2.htm

Regsvr32.exe

VB 6.0 Runtime library

Installation Instructions

Install ADO 2.0 if not yet installed

Unzip GenValidator.Zip

Check correct installation by trying Sample.exe

Interface

GenValidatorInterface.dll contains the interface that is implemented by GenValidator.dll

To use the validator in VB do the following :

To project references add ‘Generic Validator Interface V1.0’

Add code :

Dim objValidator As GenValidatorInterface.IgenValidator

Set objValidator = CreateObject("GenValidator.CValidate")

And you are ready to execute the methods of objValidator

Methods
AdoChkRule Method

Evaluates a given rule on the current record of a ado recordset. Returns true or false

Syntax

AdoChkRule(Values, Rule) As Boolean

The AdoChkRule function has these named arguments :

Part	Description
Values	Required. Ado recordset object. The values that are to be checked are represented by this recordset.
Rule	Required. String expression. Represents the rule that is checked. A string made up of one or more individual clauses concatenated with AND or OR operators

Return Values

True

False

Remarks

The Rule string is made up of clauses in the form FieldName-Operator-Value (for example, "LastName = 'Smith'"). You can create compound clauses by concatenating individual clauses with AND (for example, "LastName = 'Smith' AND FirstName = 'John'") or OR (for example, "LastName = 'Smith' OR LastName = 'Jones'"). Use the following guidelines for criteria strings:

FieldName must be a valid field name from the Recordset Values. If the field name contains spaces, you must enclose the name in square brackets.

Operator must be one of the following: <, >, <=, >=, <>, =, or LIKE.

Value is the value with which you will compare the field values (for example, 'Smith', #8/24/95#, 12.345 or $50.00). Use single quotes with strings and pound signs (#) with dates. For numbers, you can use decimal points, dollar signs, and scientific notation. If Operator is LIKE, Value can use wildcards. Only the asterisk (*) and percent sign (%) wild cards are allowed, and they must be the last character in the string. Value cannot be Null.

There is no precedence between AND and OR. Clauses can be grouped within parentheses. However, you cannot group clauses joined by an OR and then join the group to another clause with an AND, like this:

(LastName = 'Smith' OR LastName = 'Jones') AND FirstName = 'John'

Instead, you would construct this filter as

(LastName = 'Smith' AND FirstName = 'John') OR (LastName = 'Jones' AND FirstName = 'John')

In a LIKE clause, you can use a wildcard at the beginning and end of the pattern (for example, LastName Like '*mit*'), or only at the end of the pattern (for example, LastName Like 'Smit*').

AdoChkTable Method

Evaluates all rules in a rules recordset for all records in a values recordset.

Syntax

AdoChkTable(Values, Rules, RuleFieldName) As ADODB.Recordset

The AdoChkRule function has these named arguments :

Part	Description
Values	Required. Ado recordset object. The values that are to be checked are represented by this recordset.
Rules	Required. Ado recordset object. Represents the rules that are to be checked, together with custom additional fields. These could be error numbers, error descriptions, etc. One field of the recordset has to contain the rule string. This is a string made up of one or more individual clauses concatenated with AND or OR operators
RuleFieldName	Required. A string expression. Defines the fieldname of the field in the Rules recordset that contains the rule expression

Return Values

Recordset. This recordset contains all the fields of Values and all the Fields of Rules. For every combination of a rule and a record that evaluates to true a record is cretaed in the returned recordset.

Remarks

The syntax of the Rule string in the rules recordset is same as for method AdoChkRule

ArrayChkRule Method

Evaluates a given rule on a array of values. Returns true or false

Syntax

AdoChkRule(Values, Rule) As Boolean

The AdoChkRule function has these named arguments :

Part	Description
Values	Required. Array of type gvDataField. Each item of the array represents a fieldname with its data type and value.
Rule	Required. String expression. Represents the rule that is checked. A string made up of one or more individual clauses concatenated with AND or OR operators

Return Values

True

False

Remarks

gvDataField is defined as :

Type gvDataField

Datatype As gvDatatype

Fieldname As String

Value As Variant

End Type

gvDatatype is an enumaration defined as : (analogue to ado datatypes, see ado help to find correct meaning)

Public Enum gvDatatype

gvBigInt = 20

gvBinary = 128

gvBoolean = 11

gvBSTR = 8

gvChapter = 136

gvChar = 129

gvCurrency = 6

gvDate = 7

gvDBDate = 133

gvDBFileTime = 137

gvDBTime = 134

gvDBTimeStamp = 135

gvDecimal = 14

gvDouble = 5

gvEmpty = 0

gvError = 10

gvFileTime = 64

gvGUID = 72

gvIDispatch = 9

gvInteger = 3

gvIUknown = 13

gvLongVarBinary = 205

gvLongVarChar = 201

gvLongVarWChar = 203

gvNumeric = 131

gvPropVariant = 138

gvSingle = 4

gvSmallInt = 2

gvTinyInt = 16

gvUnsignedBigInt = 21

gvUnsignedInt = 19

gvUnsignedSmallInt = 18

gvUnsignedTinyInt = 17

gvUserDefined = 132

gvVarBinary = 204

gvVarChar = 200

gvVariant = 12

gvVarNumeric = 139

gvVarWChar = 202

gvWChar = 130

End Enum

The syntax of the Rule string is same as for method AdoChkRule