Appendix A: AL Syntax Reference

Objectives

By the end of this appendix you will be able to:

• Quickly look up common AL syntax and object patterns
• Reuse safe, production-oriented code templates
• Avoid beginner syntax mistakes that break compilation or runtime behavior
• Cross-reference syntax patterns used throughout Chapters 7 to 17

A.1 Core syntax cheatsheet

Object and procedure scaffolding

codeunit 50100 "Example"
{
    procedure DoWork(InputValue: Integer): Integer
    var
        Result: Integer;
    begin
        Result := InputValue + 1;
        exit(Result);
    end;
}

Conditionals and loops

if IsValid then
    Process()
else
    Error('Validation failed.');

if Rec.FindSet() then
    repeat
        HandleRec(Rec);
    until Rec.Next() = 0;

A.2 Common AL patterns (practical)

Record filtering before iteration

Installment.SetRange(Paid, false);
if Installment.FindSet() then
    repeat
        ProcessInstallment(Installment);
    until Installment.Next() = 0;

Safe state transition in trigger logic

trigger OnModify()
begin
    if xRec.Paid then
        Error('A paid installment cannot be changed.');
end;

Event subscriber scaffold

[EventSubscriber(ObjectType::Table, Database::Vendor, 'OnAfterInsertEvent', '', false, false)]
local procedure OnAfterInsertVendor(var Rec: Record Vendor)
begin
    // reaction logic
end;

A.3 Frequent syntax pitfalls

• Using = instead of := for assignment
• Forgetting begin/end for multi-line blocks
• Calling FindSet before SetRange
• Checking Rec when prior state requires xRec
• Mixing field names with inconsistent casing or quoting

A.4 Quick lookup table

Appendix summary

You now have a compact syntax reference for daily AL work and a set of practical patterns that match this book’s architecture. You can also spot and avoid common syntax and flow mistakes.

Tasks

1. Pattern matching. Pick two chapter snippets and map each to a pattern in A.2.
2. Pitfall review. Check one of your objects for at least two A.3 pitfalls.
3. Try it yourself. Add one personal syntax snippet to your local notes for future reuse.

Check your work: your selected patterns should align with Chapters 7, 9, 11, 14, and 17 practices.