coding/patterns/selectors.md

@@ -9,6 +9,38 @@
 
 [[_TOC_]]
 
+### Lookups for New() selectors
+
+\since 2112
+
+```
+const word modelType(coeffs.get<word>("type"));
+
+auto* ctorPtr = dictionaryConstructorTable(modelType);
+
+if (!ctorPtr)
+{
+    FatalIOErrorInLookup
+    (
+        dict,
+        "fvOption",
+        modelType,
+        *dictionaryConstructorTablePtr_
+    ) << exit(FatalIOError);
+}
+
+return autoPtr<option>(ctorPtr(name, modelType, coeffs, mesh));
+```
+
+This contains the following aspects:
+- The dictionary `get<word>` for retrieval with input checking
+- The lookup uses `dictionaryConstructorTable()` instead of the HashTable
+  which adds in additional checks and compatibility aliases.
+- Exit immediately upon error, leaving the _good_ case to drop through.
+- Use of the `FatalErrorInLookup` or `FatalIOErrorInLookup` macros to
+  wrap standard boilerplate text for the output.
+
+
 ### Lookups for New() selectors
 
 \since 1912
@@ -44,7 +76,7 @@ This contains the following aspects:
   but we save typing and potential mismatches by using these dedicated
   methods.
 - Exit immediately upon error, leaving the _good_ case to drop through.
-- Use of the `FatalErrorInLookup` or `FatalIOErrorInLookup` macros which
+- Use of the `FatalErrorInLookup` or `FatalIOErrorInLookup` macros to
   wrap standard boilerplate text for the output.
 
 **Anti-pattern**: The equivalent longhand version (pre-v1912)