Text input customization point allowing to ignore typed text

Author: viktorasl

MessageViewController/MessageAutocompleteController.swift

@@ -233,7 +233,7 @@ public final class MessageAutocompleteController: MessageTextViewListener {
         preserveTypingAttributes(for: textView)
     }
 
-    public func willChangeRange(textView: MessageTextView, to range: NSRange) {
+    public func willChangeText(textView: MessageTextView, inRange range: NSRange, to: String) -> Bool {
 
         // range.length == 1: Remove single character
         // range.lowerBound < textView.selectedRange.lowerBound: Ignore trying to delete
@@ -261,6 +261,7 @@ public final class MessageAutocompleteController: MessageTextViewListener {
                 })
             }
         }
+        return true
     }
 
 }

MessageViewController/MessageTextView.swift

@@ -10,7 +10,7 @@ import UIKit
 public protocol MessageTextViewListener: class {
     func didChange(textView: MessageTextView)
     func didChangeSelection(textView: MessageTextView)
-    func willChangeRange(textView: MessageTextView, to range: NSRange)
+    func willChangeText(textView: MessageTextView, inRange: NSRange, to: String) -> Bool
 }
 
 open class MessageTextView: UITextView, UITextViewDelegate {
@@ -134,8 +134,13 @@ open class MessageTextView: UITextView, UITextViewDelegate {
     }
 
     public func textView(_ textView: UITextView, shouldChangeTextIn range: NSRange, replacementText text: String) -> Bool {
-        enumerateListeners { $0.willChangeRange(textView: self, to: range) }
-        return true
+        // If listener changes text then subsequent listeners will probably get incorrect affected range
+        // and text as they were changed by previous listener. So be careful playing with textView
+        var shouldChange = true
+        // if at least one listener changes text and needs to ignore typed text then this method returns
+        // that just typed text needs to be ignored
+        enumerateListeners { shouldChange = shouldChange && $0.willChangeText(textView: self, inRange: range, to: text) }
+        return shouldChange
     }
 
 }

MessageViewController/MessageView.swift

@@ -336,6 +336,8 @@ public final class MessageView: UIView, MessageTextViewListener {
         delegate?.selectionDidChange(messageView: self)
     }
 
-    public func willChangeRange(textView: MessageTextView, to range: NSRange) {}
+    public func willChangeText(textView: MessageTextView, inRange: NSRange, to: String) -> Bool {
+        return true
+    }
 
 }