cheatsheet-variables

name	cheatsheet-variables
description	MDL Variable Cheatsheet — declaration syntax for all types, key rules, common mistakes, special values, parameter vs variable, and scope
compatibility	opencode

MDL variable reference — quick lookup for variable declarations, rules, and scope in microflows.

> Quick reference for variable declarations in MDL microflows. Covers all types (string, integer, boolean, decimal, datetime, entity, list), key rules, common mistakes, special values, and variable scope.

Load when: - Writing or debugging MDL microflow variable declarations - Getting CE0053 "Selected type is not allowed" errors - Confused about AS keyword, list syntax, or initialization requirements

<declaration_syntax>

Type	Syntax	Example
String	declare $name string = 'value';	declare $message string = '';
Integer	declare $name integer = 0;	declare $count integer = 0;
Boolean	declare $name boolean = true;	declare $IsValid boolean = true;
Decimal	declare $name decimal = 0.0;	declare $Amount decimal = 0;
DateTime	declare $name datetime = [%CurrentDateTime%];	declare $Now datetime = [%CurrentDateTime%];
Entity	declare $name as Module.Entity;	declare $Customer as Sales.Customer;
List	declare $name list of Module.Entity = empty;	declare $Orders list of Sales.Order = empty;

</declaration_syntax>

<key_rules>

1. Primitives: Use declare $var type = value; (initialization required)
2. Entities: Use declare $var as Module.Entity; (use AS keyword, no initialization)
3. Lists: Use declare $var list of Module.Entity = empty;
4. SET requires DECLARE: Always declare variables before using SET
5. Parameters are pre-declared: Microflow parameters don't need DECLARE

</key_rules>

<common_mistakes>

Entity Declaration

-- WRONG: Missing AS keyword
declare $Product Module.Product = empty;

-- CORRECT: Use AS for entity types
declare $Product as Module.Product;

SET Without DECLARE

-- WRONG: Variable not declared
if $value > 10 then
  set $message = 'High';  -- ERROR!
end if;

-- CORRECT: Declare first
declare $message string = '';
if $value > 10 then
  set $message = 'High';
end if;

List Declaration

-- WRONG: Missing 'of' keyword
declare $Items list Module.Item = empty;

-- CORRECT: Use 'list of'
declare $Items list of Module.Item = empty;

</common_mistakes>

<special_values>

Value	Usage
empty	Null/empty value for any type
[%CurrentDateTime%]	Current date and time
[%CurrentUser%]	Currently logged in user object
true / false	Boolean literals

</special_values>

<parameter_vs_variable>

create microflow Module.Example (
  $Input: string,              -- Parameter: auto-declared
  $entity: Module.Customer     -- Parameter: auto-declared
)
returns boolean
begin
  -- Parameters $Input and $Entity are already available

  declare $Result boolean = true;  -- Local variable: must declare
  declare $Temp as Module.Order;   -- Local entity: must declare

  return $Result;
end;
/

</parameter_vs_variable>

<variable_scope>

• Parameters: Available throughout the microflow
• DECLARE variables: Available from declaration point forward
• Loop variables: Only available inside the loop body

loop $item in $ItemList
begin
  -- $item is available here (derived from list type)
  set $count = $count + 1;
end loop;
-- $item is NOT available here

</variable_scope>

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