使用 UITextPosition，从 textInRange 获取前一个字符

Question

我一直在寻找高位和低位，无法弄清楚如何做到这一点。假设我有一个这样的字符串：

NSString *string = @"&foo !foo";

我要做的是区分文本视图中的两个 foos（听起来很有趣哈哈）。当我单击一个时，我想知道哪个（& 或！）出现在它之前。我是这样理解的：

UITapGestureRecognizer *recognizer = (UITapGestureRecognizer *)sender;
UITextView *TV = (UITextView*)recognizer.view;
CGPoint location = [recognizer locationInView:TV];
location.y += TV.contentOffset.y;
UITextPosition *tapPosition = [TV closestPositionToPoint:CGPointMake(location.x, location.y)];
UITextRange *textRange = [TV.tokenizer rangeEnclosingPosition:tapPosition 
    withGranularity:UITextGranularityWord inDirection:UITextLayoutDirectionRight];
NSString *tappedWord = [TV textInRange:textRange];

我不知道如何获得前一个字符。 TV.tokenizer UITextGranularityCharacter 只得到最接近的字母，而不是符号。有什么解决办法吗？

Answer 1

检查：Convert selectedTextRange UITextRange to NSRange 将您的UITextRange 转换为NSRange（我将调用selectedRange）。

对链接问题的上一个答案启发了我，您需要在代码末尾添加以下内容：

UITextPosition *beginning = TV.beginningOfDocument;
UITextPosition *selectionStart = textRange.start;
UITextPosition *selectionEnd = textRange.end;
NSInteger location = [TV offsetFromPosition:beginning toPosition:selectionStart];
NSInteger length = [TV offsetFromPosition:selectionStart toPosition:selectionEnd];
NSRange selectedRange = NSMakeRange(location,lenght);
NSRange range = NSMakeRange(selectedRange.location-1,1) //Maybe need to check if selectedRange.location>0
NSString *yourCharString = [[TV text] substringWithRange:range];