From 17415938c7180a95811db949122b8ad24a442866 Mon Sep 17 00:00:00 2001
From: zhongwuzw <zhongwuzw@qq.com>
Date: Tue, 12 Mar 2019 11:04:55 -0700
Subject: [PATCH] Fix TextInput maxLength when insert characters at begin
 (#23472)

Summary:
Fixes #21639 , seems we tried to fix this before, please see related `PR` like [D10392176](https://github.com/facebook/react-native/commit/36507e4a3c2fa58dcfdc9bd389b37536c66006d0), #18627, but they don't solve it totally.

[iOS] [Fixed] - Fix TextInput maxLength when insert characters at begin
Pull Request resolved: https://github.com/facebook/react-native/pull/23472

Reviewed By: mmmulani

Differential Revision: D14366406

Pulled By: ejanzer

fbshipit-source-id: fc983810703997b48824f84f2f9198984afba9cd
---
 Libraries/Text/TextInput/RCTBaseTextInputView.m | 15 ++++-----------
 1 file changed, 4 insertions(+), 11 deletions(-)

diff --git a/Libraries/Text/TextInput/RCTBaseTextInputView.m b/Libraries/Text/TextInput/RCTBaseTextInputView.m
index 0a8ea15b7c0eaf..e10e508f0904d1 100644
--- a/Libraries/Text/TextInput/RCTBaseTextInputView.m
+++ b/Libraries/Text/TextInput/RCTBaseTextInputView.m
@@ -398,18 +398,12 @@ - (BOOL)textInputShouldChangeTextInRange:(NSRange)range replacementText:(NSStrin
     }
   }
 
-  if (range.location + range.length > _predictedText.length) {
-    // _predictedText got out of sync in a bad way, so let's just force sync it.  Haven't been able to repro this, but
-    // it's causing a real crash here: #6523822
+  NSString *previousText = backedTextInputView.attributedText.string ?: @"";
+  
+  if (range.location + range.length > backedTextInputView.attributedText.string.length) {
     _predictedText = backedTextInputView.attributedText.string;
-  }
-
-  NSString *previousText = [_predictedText substringWithRange:range] ?: @"";
-
-  if (!_predictedText || backedTextInputView.attributedText.string.length == 0) {
-    _predictedText = text;
   } else {
-    _predictedText = [_predictedText stringByReplacingCharactersInRange:range withString:text];
+    _predictedText = [backedTextInputView.attributedText.string stringByReplacingCharactersInRange:range withString:text];
   }
 
   if (_onTextInput) {
@@ -444,7 +438,6 @@ - (void)textInputDidChange
     [self textInputShouldChangeTextInRange:predictionRange replacementText:replacement];
     // JS will assume the selection changed based on the location of our shouldChangeTextInRange, so reset it.
     [self textInputDidChangeSelection];
-    _predictedText = backedTextInputView.attributedText.string;
   }
 
   _nativeEventCount++;