Validation

Overview

A Validation Logic Block is a business rule that yields a boolean output—either true (valid) or false (invalid). Validations are used extensively to verify input values, check preconditions, and ensure post-conditions are met.

Validations are essential for:

• Input Validation: Ensuring data entered by users meets requirements
• Preconditions: Verifying conditions are met before an action proceeds
• Post-conditions: Confirming expected state after an action completes
• Business Rule Enforcement: Ensuring data complies with business policies

Structure

A Validation consists of:

Component	Description
Name	Unique identifier for the validation
Description	What the validation checks
Inputs	Data to validate
Output	Boolean (true = valid, false = invalid)
Validation Expression	The rule to evaluate
Error Message	Message to display when validation fails

Live Demo

Type an email address and watch each rule in the validation expression evaluate in real time.

✓ValidateEmailValidation● AUTO

Email

Validation Expression

○Not empty

○Contains @

○Contains a domain

○Min 5 characters

Validation Expression

The validation expression evaluates to true when the data is valid, false when invalid. Expressions use the Flowon Expression Language—the same language used in Formulas.

Common Validation Patterns

Pattern	Description	Example
Required Field	Value must be provided	Value != null && Value != ""
Range Check	Value within bounds	Amount >= MinAmount && Amount <= MaxAmount
Pattern Match	Value matches format	MATCHES(Email, emailPattern)
Date Range	Dates in correct order	StartDate <= EndDate
Conditional Requirement	Required based on condition	IF(Status == "Approved", ApprovalDate != null, true)
Cross-Field Validation	Fields must be consistent	Total == SUM(LineItems)

Expression Language Reference

For complete documentation of all functions and operators available in validation expressions, see the Flowon Expression Language Reference.

Example: Email Validation

Name: ValidateEmail

Inputs:

• Email (String): Email address to validate

Output:

• IsValid (Boolean)

Validation Expression:

Email != null 
&& Email != "" 
&& CONTAINS(Email, "@") 
&& CONTAINS(Email, ".")
&& LEN(Email) >= 5

Error Message: "Please enter a valid email address"

Example: Order Validation

Name: ValidateOrderForSubmission

Inputs:

• OrderDate (DateTime): When order was placed
• RequestedDeliveryDate (DateTime): When customer wants delivery
• TotalAmount (Money): Order total
• CustomerCreditLimit (Money): Customer's credit limit
• HasApprovedProducts (Boolean): Whether all products are approved for sale

Output:

• IsValid (Boolean)

Validation Expression:

OrderDate != null
&& RequestedDeliveryDate > OrderDate
&& ADDDAYS(OrderDate, 3) <= RequestedDeliveryDate
&& TotalAmount > 0
&& TotalAmount <= CustomerCreditLimit
&& HasApprovedProducts == true

Error Message: "Order cannot be submitted. Check delivery date (min 3 days), credit limit, and product availability."

Example: Date Range Validation

Name: ValidateDateRange

Inputs:

• StartDate (DateTime): Beginning of period
• EndDate (DateTime): End of period
• MaxDurationDays (Integer): Maximum allowed duration

Output:

• IsValid (Boolean)

Validation Expression:

StartDate != null
&& EndDate != null
&& StartDate <= EndDate
&& DATEDIFF(StartDate, EndDate) <= MaxDurationDays

Error Message: "Invalid date range. End date must be after start date and within the maximum duration."