From f9d9d2c8115da469c234768c220205feb2a58eb1 Mon Sep 17 00:00:00 2001
From: Sepandar Derakhshandeh <69620649+Sepandard@users.noreply.github.com>
Date: Fri, 22 Nov 2024 11:36:24 +0330
Subject: [PATCH] fix(docs): update errorState example to cover handle missing
 state (#30059)

resolves #29750

(cherry picked from commit 23c19be3534d5dd64fc8b1106fa9a33e30ae4f64)
---
 guides/creating-a-custom-form-field-control.md | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/guides/creating-a-custom-form-field-control.md b/guides/creating-a-custom-form-field-control.md
index a4b66adf0ecb..3911d17073ab 100644
--- a/guides/creating-a-custom-form-field-control.md
+++ b/guides/creating-a-custom-form-field-control.md
@@ -357,14 +357,14 @@ ngDoCheck() {
 }
 
 private updateErrorState() {
-  const parent = this._parentFormGroup || this.parentForm;
+  const parentSubmitted = this._parentFormGroup?.submitted || this._parentForm?.submitted;
+  const touchedOrParentSubmitted = this.touched || parentSubmitted;
 
-  const oldState = this.errorState;
-  const newState = (this.ngControl?.invalid || this.parts.invalid) && (this.touched || parent.submitted);
+  const newState = (this.ngControl?.invalid || this.parts.invalid) && touchedOrParentSubmitted;
 
-  if (oldState !== newState) {
+  if (this.errorState !== newState) {
     this.errorState = newState;
-    this.stateChanges.next();
+    this.stateChanges.next(); // Notify listeners of state changes.
   }
 }
 ```