关于键盘输入中文控制字数 （找了很久，最好的写法）真是完美

- (void)textchanged:(NSNotification *)noti{

    UITextField *textfield = (UITextField *)noti.object;

    NSInteger kMaxLength = 40;

    if (textfield.tag == kSuggestAdressFieldTag) {

        kMaxLength = 20;

    }

    NSString *toBeString =textfield.text;

    NSString *lang = [[UITextInputMode currentInputMode] primaryLanguage];

    if([lang isEqualToString:@"zh-Hans"]){ //简体中文输入，包括简体拼音，健体五笔，简体手写

        UITextRange *selectedRange = [textfield markedTextRange];

        UITextPosition *position = [textfield positionFromPosition:selectedRange.start offset:0];

        if (!position){//非高亮

            if (toBeString.length > kMaxLength) {

                textfield.text = [toBeString substringToIndex:kMaxLength];

            }

        }

    }else{//中文输入法以外

        if (toBeString.length > kMaxLength) {

           textfield.text = [toBeString substringToIndex:kMaxLength];

        }

    }

}

关于键盘输入中文控制字数 （找了很久，最好的写法）真是完美

原文：http://www.cnblogs.com/MaybeQueen/p/4831812.html