[TextControls] Add MDCBaseTextFieldDelegate

PiperOrigin-RevId: 324075961

components/TextControls/src/BaseTextFields/MDCBaseTextField.h

@@ -16,6 +16,8 @@
 
 #import "MaterialTextControls+Enums.h"
 
+@protocol MDCBaseTextFieldDelegate;
+
 /**
  The superclass of MDCFilledTextField and MDCOutlinedTextField. While not forbidden by the compiler,
  subclassing this class is not supported and is highly discouraged.
@@ -175,6 +177,11 @@
  */
 @property(nonatomic, assign) CGFloat preferredContainerHeight;
 
+/**
+ This delegate receives text field related updates not covered by @c UITextFieldDelegate.
+ */
+@property(nonatomic, weak, nullable) id<MDCBaseTextFieldDelegate> baseTextFieldDelegate;
+
 @end
 
 @interface MDCBaseTextField (UIAccessibility)

components/TextControls/src/BaseTextFields/MDCBaseTextField.m

@@ -18,6 +18,7 @@
 
 #import <MDFInternationalization/MDFInternationalization.h>
 
+#import "MDCBaseTextFieldDelegate.h"
 #import "MaterialMath.h"
 #import "MaterialTextControlsPrivate+BaseStyle.h"
 #import "MaterialTextControlsPrivate+Shared.h"
@@ -743,4 +744,13 @@ - (nonnull UIColor *)trailingAssistiveLabelColorForState:(MDCTextControlState)st
   return colorViewModel.trailingAssistiveLabelColor;
 }
 
+#pragma mark UIKeyInput
+
+- (void)deleteBackward {
+  [super deleteBackward];
+  if ([_baseTextFieldDelegate respondsToSelector:@selector(baseTextFieldDidDeleteBackward:)]) {
+    [_baseTextFieldDelegate baseTextFieldDidDeleteBackward:self];
+  }
+}
+
 @end

components/TextControls/src/BaseTextFields/MDCBaseTextFieldDelegate.h

@@ -0,0 +1,35 @@
+// Copyright 2020-present the Material Components for iOS authors. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#import <UIKit/UIKit.h>
+
+@class MDCBaseTextField;
+
+/**
+This delegate protocol for @c MDCBaseTextField and its subclasses provides updates not already
+covered by @c UITextFieldDelegate.
+ */
+@protocol MDCBaseTextFieldDelegate <NSObject>
+
+@optional
+
+/**
+ This method is called at the end of @c MDCBaseTextField's implementation of @c -deleteBackward.
+
+ @param textField The MDCBaseTextField calling @c -deleteBackward.
+ */
+- (void)baseTextFieldDidDeleteBackward:(MDCBaseTextField *)textField;
+;
+
+@end

components/TextControls/src/BaseTextFields/MaterialTextControls+BaseTextFields.h

@@ -13,3 +13,4 @@
 // limitations under the License.
 
 #import "MDCBaseTextField.h"
+#import "MDCBaseTextFieldDelegate.h"