🎯 Understanding Uniface 10.4 Parameter Blocks: A Developer's Guide

Working with Uniface can be challenging, especially when it comes to understanding parameter declarations. Let's dive deep into the params...endparams block and explore how to effectively use parameter definitions in your Uniface 10.4 applications! 🚀

This article is based on the official Uniface Documentation 10.4, and AI assistance helped me structure this comprehensive guide.

📋 What is the params Block?

The params...endparams block is fundamental in Uniface development. It defines formal parameters for:

• 🔧 Operations
• ⚙️ Functions (global or local ProcScript modules)
• 🌍 Global ProcScripts

🛠️ Basic Syntax Structure

params
  DataType ParamName : Direction
   {DataType} Field.Entity{.Model} : Direction
   {DataType} $ComponentVariable$ : Direction
   {byRef} | {byVal} struct ParamName : Direction
   entity Entity{.Model} : Direction
   occurrence Entity{.Model} : Direction
   xmlstream [DTD:DTDName]ParamName : Direction
endparams

📊 Key Parameter Elements

Element	Description	Example
DataType	Uniface data type (string, numeric, etc.)	string, numeric
ParamName	Max 32 bytes, letters, digits, underscores	CUSTID, AMOUNT_TOTAL
Direction	Parameter flow direction	IN, OUT, INOUT

🎯 Parameter Directions Explained

📥 IN Parameters

Input only - data flows from caller to operation

📤 OUT Parameters

Output only - data flows from operation back to caller. Warning: Initial value is unpredictable! ⚠️

🔄 INOUT Parameters

Bidirectional - data flows both ways

🏗️ Special Parameter Types

📦 Struct Parameters

Structs can be passed by reference (byRef) or by value (byVal):

• byRef: Only memory pointer is passed - faster but same process required
• byVal: Complete data copy - slower but works across processes

🗃️ Entity and Occurrence Parameters

These are "constructed parameters" that transfer entity data between components:

• entity: Transfers ALL occurrences of an entity 📚
• occurrence: Transfers only the CURRENT occurrence 📄

🌐 XML Stream Parameters

Handle XML data with optional DTD validation using xmlstream parameters.

💡 Practical Example

Here's a real-world example of a discount calculation operation:

operation DISCOUNT
params
  string CUSTID : IN
  numeric AMOUNT : INOUT
  numeric PERCENTAGE : OUT
endparams

; Calculate discount based on customer
PERCENTAGE = 0
if ( CUSTID == "ufbv" ) PERCENTAGE = 20
if ( CUSTID == "acme" ) PERCENTAGE = 15
AMOUNT = AMOUNT * ( 100 - PERCENTAGE) / 100
end

This operation can be called like this:

activate "SERV1".DISCOUNT (ID.CUST, TOTAL.INVOICE, $DISCOUNT$)

🔍 Important Limitations and Rules

• 📏 Maximum 64 parameters per operation
• 💾 Maximum parameter size: 10 MB
• 🚫 Constructed parameters can't be used in functions
• ⚠️ Avoid OUT/INOUT parameters with asynchronous activation
• 🔒 Cross-process byRef struct parameters will cause errors

🎯 Parameter Scope Rules

Understanding scope is crucial:

• Component-level: Entity, occurrence, field, and component variable parameters 🌍
• Operation-level: Named parameters exist only within their operation/module 🏠
• Name conflicts: Parameters take precedence over fields with the same name 🥊

🚀 Best Practices

1. Always explicitly specify byRef or byVal for struct parameters
2. Use qualified field names when parameter names conflict with field names
3. Consider memory implications when choosing between byRef and byVal
4. Document your parameter directions clearly for team collaboration
5. Test cross-process scenarios thoroughly when using struct parameters

🎉 Conclusion

Mastering Uniface parameter blocks is essential for building robust, maintainable applications. The flexibility of different parameter types and directions gives you powerful tools for component communication, but with great power comes great responsibility! 💪

Happy coding with Uniface 10.4! 🎊