See: OCLOperators_scripteval

ScriptEvalCheck is a validation operator used in the Executable Action Language (EAL). It parses a string as OCL and verifies its syntax and type-compatibility against a specific model context without actually executing the logic or changing data.

Syntax

self.ScriptEvalCheck(IsQuery: Boolean, ReturnType: Type, Expression: String): String

• IsQuery: Set to false for standard actions or true for read-only evaluations.
• ReturnType: The expected model type (e.g., Decimal, String, Integer) that the expression must return.
• Expression: The String attribute or literal containing the OCL code.

1. Implementation Logic

In your Action Editor, you implement ScriptEvalCheck as the condition in a let statement. This allows you to store the "check result" as a variable before deciding whether to proceed with the actual evaluation.

Action OCL Syntax:

Object Constraint Language

-- 'validationInfo' will hold the result of the check
let validationInfo = self.ScriptEvalCheck(false, Decimal, self.DynamicFormula) in
(
  -- If the script is valid, 'validationInfo' is exactly 'ok'
  if validationInfo = 'ok' then
     -- SAFE TO EXECUTE
     self.FormulaResult := self.ScriptEval(false, Decimal, self.DynamicFormula).asstring
  else
     -- UNSAFE: Store the error message so the user can see what's wrong
     self.FormulaResult := validationInfo
  endif
)

2. How it Works

When you call ScriptEvalCheck, MDriven performs three background tasks:

• Syntax Scan: It checks if the string in self.DynamicFormula is valid OCL (e.g., no missing brackets or misspelled operators).
• Type Verification: It ensures the script returns the type you requested (in our case, Decimal).
• Context Check: It confirms that all properties referenced (like self.Total) exist on the Order class.

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3. Visualizing Failure vs. Success

Implementing this operator is what created the "Work Visualization" we saw in your screenshots:

• Failure Implementation: When the formula was 'self.Total * 0.10', ScriptEvalCheck identified a type mismatch between Decimal and Double. It returned a long error string, which you successfully displayed in the FormulaResult box.
• Success Implementation: When you corrected the formula to 'self.Total * 0.10.ToDecimal', ScriptEvalCheck found no issues and returned the string 'ok'. This allowed the if statement to trigger the actual ScriptEval.