patterns-crud

name	patterns-crud
description	Standard CRUD microflow patterns for Mendix: Save, Validate, Delete, Cancel, New, Edit, and DataSource microflows with naming conventions
compatibility	opencode

CRUD microflow pattern expert for Mendix. Covers Save, Validate, Delete, Cancel, New, Edit, and DataSource patterns with naming conventions and best practices.

Standard patterns for Create, Read, Update, Delete operations on entities.

- Write CRUD action microflows for an entity - Create validation microflows - Implement save, delete, cancel, or new patterns - Set up data source microflows for grids and lists

<naming_conventions>

Prefix	Purpose	Example
ACT_	Action microflow (page button)	ACT_Customer_Save
VAL_	Validation microflow	VAL_Customer_Save
DS_	Data source microflow	DS_Customer_GetAll
SUB_	Sub-microflow (internal)	SUB_Customer_SendEmail
</naming_conventions>

<save_pattern>

/**
 * Save action for Customer NewEdit page
 * Validates, commits, and closes the page
 *
 * @param $Customer The customer to save
 * @returns true if saved successfully
 */
create microflow Module.ACT_Customer_Save (
  $Customer: Module.Customer
)
returns boolean
begin
  -- Validate first
  declare $IsValid boolean = true;
  $IsValid = call microflow Module.VAL_Customer_Save($Customer = $Customer);

  if $IsValid then
    commit $Customer with events;
    close page;
  end if;

  return $IsValid;
end;
/

</save_pattern>

<validation_pattern>

/**
 * Validate Customer before save
 *
 * @param $Customer The customer to validate
 * @returns true if valid
 */
create microflow Module.VAL_Customer_Save (
  $Customer: Module.Customer
)
returns boolean
begin
  declare $IsValid boolean = true;

  -- Required field validation
  if $Customer/Name = empty then
    validation feedback $Customer/Name message 'Name is required';
    set $IsValid = false;
  end if;

  if $Customer/Email = empty then
    validation feedback $Customer/Email message 'Email is required';
    set $IsValid = false;
  end if;

  -- Business rule validation
  if $Customer/CreditLimit < 0 then
    validation feedback $Customer/CreditLimit message 'Credit limit cannot be negative';
    set $IsValid = false;
  end if;

  return $IsValid;
end;
/

</validation_pattern>

<delete_pattern>

/**
 * Delete a customer
 * Called after user confirms deletion
 *
 * @param $Customer The customer to delete
 * @returns true if deleted
 */
create microflow Module.ACT_Customer_Delete (
  $Customer: Module.Customer
)
returns boolean
begin
  delete $Customer;
  close page;
  return true;
end;
/

</delete_pattern>

<cancel_pattern>

/**
 * Cancel editing and close page
 * Discards uncommitted changes
 *
 * @param $Customer The customer being edited
 * @returns true
 */
create microflow Module.ACT_Customer_Cancel (
  $Customer: Module.Customer
)
returns boolean
begin
  rollback $Customer;
  close page;
  return true;
end;
/

</cancel_pattern>

<create_new_pattern>

/**
 * Create new customer and open edit page
 *
 * @returns true
 */
create microflow Module.ACT_Customer_New ()
returns boolean
begin
  declare $NewCustomer as Module.Customer;

  $NewCustomer = create Module.Customer (
    IsActive = true,
    CreatedDate = [%CurrentDateTime%]
  );

  show page Module.Customer_NewEdit ($Customer = $NewCustomer);
  return true;
end;
/

</create_new_pattern>

<data_source_pattern>

/**
 * Get all active customers
 * Used as data source for Customer overview
 *
 * @returns List of active customers
 */
create microflow Module.DS_Customer_GetActive ()
returns list of Module.Customer
begin
  declare $Customers list of Module.Customer = empty;

  retrieve $Customers from Module.Customer
    where IsActive = true;

  return $Customers;
end;
/

</data_source_pattern>

<edit_pattern>

/**
 * Open customer for editing
 *
 * @param $Customer The customer to edit
 * @returns true
 */
create microflow Module.ACT_Customer_Edit (
  $Customer: Module.Customer
)
returns boolean
begin
  show page Module.Customer_NewEdit ($Customer = $Customer);
  return true;
end;
/

</edit_pattern>

<complete_crud_set> For a typical entity, create these microflows:

Microflow	Purpose	Parameters
ACT_Entity_New	Create new	None
ACT_Entity_Edit	Open for edit	$entity
ACT_Entity_Save	Save changes	$entity
VAL_Entity_Save	Validate	$entity
ACT_Entity_Delete	Delete	$entity
ACT_Entity_Cancel	Cancel edit	$entity
DS_Entity_GetAll	List all	None
</complete_crud_set>

<best_practices>

1. Always validate before commit: Call VAL_ microflow in ACT_Save
2. Use WITH EVENTS: commit $entity with events triggers event handlers
3. Close page on success: Use close page after successful save/delete
4. Rollback on cancel: Use rollback $entity to discard changes
5. Initialize defaults: Set default values in ACT_New microflow
6. Return Boolean: All action microflows should return success status </best_practices>

<output_rules>Output MDL code only in code blocks. Keep explanations concise.</output_rules>