Generic Validator Method Pattern
Generic Validator Method Pattern is a design pattern which is an extension of Generic Method Pattern. Purpose of this design pattern is to validate one or more entities in a specific context. This is a very commonly used pattern in other languages, just that it is adjusted to Generic Method Pattern.
Generic Method Pattern
It has a public method and two business events which can be subscribed to change or extend the behaviour of the method.
Public Method may contain the following sequence of calls:
UI Confirmation (Optional)
OnBefore Business Event
Execute Logic
OnAfter Business Event
UI Acknowledgement (Optional)
Generic Method Pattern better explained in "Design patterns for developing repeatable IP for Dynamics 365 Business Central"
Generic Validator Method Pattern
It has two public methods and two business events which can be subscribed to change or extend the behaviour of the method.
This pattern contains HasErrors and Validate public functions.
HasErrors Method
This method will check validation errors in the entity and stores errors in Errors parameter and returns true if there are any validation errors.
This method should contain the following sequence of calls:
OnBefore Business Event
Execute Logic
OnAfter Business Event
Validate Method
This method will throw a multi line error message with all validation errors found in HasErrors method.
Sample Code
codeunit 50101 CreateSalesOrderValidator
{
procedure Validate(Customer: Record Customer)
var
Errors: List of [Text];
begin
if HasErrors(Customer, Errors) then
Error(ErrorsToText(Errors));
end;
procedure HasErrors(Customer: Record Customer; Errors: List of [Text]): Boolean
var
Handled: Boolean;
begin
OnBeforeCreateSalesOrderValidator(Customer, Handled);
DoCreateSalesOrder(Customer, Errors, Handled);
OnAfterCreateSalesOrderValidator(Customer);
if Errors.Count() > 0 then
exit(true);
end;
local procedure ErrorsToText(Errors: List of [Text]): Text
var
ErrText: Text;
TxtBuffer: TextBuilder;
begin
foreach ErrText in Errors do
TxtBuffer.AppendLine(ErrText);
exit(TxtBuffer.ToText());
end;
local procedure DoCreateSalesOrder(Customer: Record Customer; Errors: List of [Text]; Handled: Boolean)
begin
if Handled then
exit;
ValidateGenBusinessPostingGroup(Customer, Errors);
ValidateVATBusPostingGroup(Customer, Errors);
ValidateVATRegistrationNo(Customer, Errors);
end;
local procedure ValidateGenBusinessPostingGroup(Customer: Record Customer; Errors: List of [Text])
var
GenBusPostingGroupErr: Label 'Gen. Bus. Posting Group should not be empty.';
begin
if Customer."Gen. Bus. Posting Group" = '' then
Errors.Add(GenBusPostingGroupErr);
end;
local procedure ValidateVATBusPostingGroup(Customer: Record Customer; Errors: List of [Text])
var
GenBusPostingGroupErr: Label 'VAT Bus. Posting Group should not be empty.';
begin
if Customer."VAT Bus. Posting Group" = '' then
Errors.Add(GenBusPostingGroupErr);
end;
local procedure ValidateVATRegistrationNo(Customer: Record Customer; Errors: List of [Text])
var
GenBusPostingGroupErr: Label 'Customer should have a valid VAT Registration No.';
begin
if Customer."VAT Registration No." = '' then
Errors.Add(GenBusPostingGroupErr);
end;
[BusinessEvent(false)]
local procedure OnBeforeCreateSalesOrderValidator(Customer: Record Customer; var Handled: Boolean)
begin
end;
[BusinessEvent(false)]
local procedure OnAfterCreateSalesOrderValidator(Customer: Record Customer)
begin
end;
}Use Cases
This pattern can be used in the following senarios:
Postings, Actions
Validate Transactional Entities before posting or before performaning an action.
APIs, Web Services
Validating Entities before importing or accepting data via APIs or Web Services.
#MSDyn365 #MSDyn365BC #BusinessCentral #DynamicsNAV #DesignPatterns
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