uitextview クラスのメソッドをオーバーライドしようとしていますが、作業中のクラスでそれを行いたいのですが、動作させることができません。私は人々が別のクラスでそれをオーバーライドするのを見ただけです。ありがとうございました。
   #import <UIKit/UIKit.h>
@interface MyTextView : UITextView
@end
@interface ViewController : UIViewController
@property (nonatomic, retain) IBOutlet MyTextView * tv;
@end
//////////////////////////////////
   #import "ViewController.h"
@implementation MyTextView
- (BOOL)canPerformAction:(SEL)action withSender:(id)sender    
{    
    [UIMenuController sharedMenuController].menuVisible = NO;  //do not display the menu
   // [self resignFirstResponder];                      //do not allow the user to selected anything
    return NO;
}
@end
@implementation ViewController
@synthesize tv;
- (void)viewDidLoad
{
    [super viewDidLoad];
    tv = [[MyTextView alloc] init];
    // Do any additional setup after loading the view, typically from a nib.
}
- (void)viewDidUnload
{
    [super viewDidUnload];
    // Release any retained subviews of the main view.
}
- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation
{
    if ([[UIDevice currentDevice] userInterfaceIdiom] == UIUserInterfaceIdiomPhone) {
        return (interfaceOrientation != UIInterfaceOrientationPortraitUpsideDown);
    } else {
        return YES;
    }
}
-(void)textViewDidChangeSelection:(MyTextView *)textView
{
    NSRange range = textView.selectedRange;
    if(range.location<textView.text.length)
    {
        NSString * getRidOfFirstHalfString = [tv.text substringFromIndex:range.location];
        NSString * selectedString = [getRidOfFirstHalfString substringToIndex:range.length];
        NSLog(@"%@",selectedString);
    }
    else
    {
        // Do what ever you want to do
    }   
}
@end