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UITextViewで一文字ずつUndo/Redoする方法

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UITextViewには標準でUndo/Redoの機能があります。しかし、その単位が単語となっているため、必ずしも使いやすくありません。これを一文字単位でUndo/Redoする方法を発見しました。

以下のコードを書いて、どこかでsetupHook()を呼びます。するとその後、概ね一文字ずつ逐次Undo/Redoされるようになります。

(追記:日本語のように変換を介するものも逐次Undo/Redoできる方法も発見しました。)


ObjectiveC

#import <objc/runtime.h>


@implementation UITextView (hook)
- (void)myReplaceRange:(UITextRange *)range withText:(NSString *)text
{
[self.undoManager beginUndoGrouping];
[self myReplaceRange:range withText:text];
[self.undoManager endUndoGrouping];
}

- (void)mySetMarkedText:(NSString *)text selectedRange:(NSRange)range
{
if (0 < text.length) {
[self.undoManager beginUndoGrouping];
[self mySetMarkedText:text selectedRange:range];
[self.undoManager endUndoGrouping];
}
}

-(void)myInsertText:(NSString *)text
{
[self.undoManager beginUndoGrouping];
[self myInsertText:text];
[self.undoManager endUndoGrouping];
}

-(void)myDeleteBackward
{
[self.undoManager beginUndoGrouping];
[self myDeleteBackward];
[self.undoManager endUndoGrouping];
}
@end

void setupHook()
{
static BOOL install = NO;
if (!install) {
install = YES;
Class klass = [UITextView class];
Method orgMethod = class_getInstanceMethod(klass, @selector(replaceRange:withText:));
Method myMethod = class_getInstanceMethod(klass, @selector(myReplaceRange:withText:));
method_exchangeImplementations(orgMethod, myMethod);
orgMethod = class_getInstanceMethod(klass, @selector(setMarkedText:selectedRange:));
myMethod = class_getInstanceMethod(klass, @selector(mySetMarkedText:selectedRange:));
method_exchangeImplementations(orgMethod, myMethod);
orgMethod = class_getInstanceMethod(klass, @selector(insertText:));
myMethod = class_getInstanceMethod(klass, @selector(myInsertText:));
method_exchangeImplementations(orgMethod, myMethod);
orgMethod = class_getInstanceMethod(klass, @selector(deleteBackward));
myMethod = class_getInstanceMethod(klass, @selector(myDeleteBackward));
method_exchangeImplementations(orgMethod, myMethod);
}