if not then exit

content/docs/BestPractices/if-not-find-then-exit/index.md

@@ -0,0 +1,99 @@
+---
+title: "if not then exit"
+tags: ["AL"]
+categories: ["Best Practice"]
+---
+
+_Created by sirhc101, Described by sirhc101_
+
+## Description
+
+In general when we are working with tables we want to make sure, the filtered dataset includes records and does not result in a runtime error, so we use `if` to handle the result of `Find()`, `FindSet()`, `Get()`, etc.
+This automatically causes on indent in source code and often the source code does not just contain one but two or more tables involved which leads to multi-level indentation.
+
+Basically this is a result of bad coding structure but maybe sometimes necessary. On the other hand this causes multiple `end;` usages and leads to the usage of colorization and other helpers to see which `begin` belongs to which `end;`.
+
+Instead of using `if (Record.FindSet()) then` to fetch records from a database it's good practice to use `if (not Record.FindSet()) then` following by an `exit();` to not further process the source code and make it clear for other developers where they can stop reading in certain cases.
+
+Furthermore, this more or less automatically leads to smaller and better structured procedures and reduces the complexity of the source code.
+
+## Bad code
+
+```al
+    SalesHeader.Reset();
+    SalesHeader.SetRange("Document Type", SalesHeader."Document Type"::Order);
+    SalesHeader.SetRange(Status, SalesHeader.Status::Open);
+    if (SalesHeader.FindSet(false)) then begin
+        repeat
+            SalesLine.Reset();
+            SalesLine.SetRange("Document Type", SalesHeader."Document Type"::Order);
+            SalesLine.SetRange("Document No.", SalesHeader."No.");
+            if (SalesLine.FindSet(true)) then begin
+                repeat
+                    DoSomething();
+                until SalesLine.Next() = 0;
+            end;
+        until SalesHeader.Next() = 0;
+
+        DoSomethingElse();
+    end;
+```
+
+or
+
+```al
+    SalesLine.Reset();
+    SalesLine.SetRange("Document Type", SalesHeader."Document Type"::Order);
+    if (SalesLine.FindSet(true)) then begin
+        repeat
+            case SalesLine."Type" of
+                SalesLine."Type"::Item:
+                    DoSomethingItem();
+                SalesLine."Type"::Resource:
+                    DoSomethingResource();
+            end;
+        until SalesLine.Next() = 0;
+    end;
+```
+
+## Good code
+
+```al
+    SalesHeader.Reset();
+    SalesHeader.SetRange("Document Type", SalesHeader."Document Type"::Order);
+    SalesHeader.SetRange(Status, SalesHeader.Status::Open);
+    if (not SalesHeader.FindSet(false)) then
+        exit;
+
+    repeat
+        SalesLine.Reset();
+        SalesLine.SetRange("Document Type", SalesHeader."Document Type"::Order);
+        SalesLine.SetRange("Document No.", SalesHeader."No.");
+        if (SalesLine.FindSet(true)) then begin
+            repeat
+                DoSomething();
+            until SalesLine.Next() = 0;
+        end;
+    until SalesHeader.Next() = 0;
+
+    DoSomethingElse();
+end;
+```
+
+or
+
+```al
+    SalesLine.Reset();
+    SalesLine.SetRange("Document Type", SalesHeader."Document Type"::Order);
+    if (not SalesLine.FindSet(true)) then
+        exit;
+
+    repeat
+        case SalesLine."Type" of
+            SalesLine."Type"::Item:
+                DoSomethingItem();
+            SalesLine."Type"::Resource:
+                DoSomethingResource();
+        end;
+    until SalesLine.Next() = 0;
+```