IOS -->> 给UITextView增加链接

现在在iOS添加你自己的Twitter账户更加简单了，现在你可以给一个NSAttributedString增加链接了，然后当它被点击的时候唤起一个定制的action。

首先，创建一个NSAttributedString然后增加给它增加一个NSLinkAttributeName 属性，见以下：

NSMutableAttributedString *attributedString = [[NSMutableAttributedString alloc] initWithString:@"This is an example by @marcelofabri_"];
[attributedString addAttribute:NSLinkAttributeName
                         value:@"username://marcelofabri_"
                         range:[[attributedString string] rangeOfString:@"@marcelofabri_"]]; 

NSDictionary *linkAttributes = @{NSForegroundColorAttributeName: [UIColor greenColor],
                                 NSUnderlineColorAttributeName: [UIColor lightGrayColor],
                                 NSUnderlineStyleAttributeName: @(NSUnderlinePatternSolid)}; 

// assume that textView is a UITextView previously created (either by code or Interface Builder)
textView.linkTextAttributes = linkAttributes; // customizes the appearance of links
textView.attributedText = attributedString;
textView.delegate = self; 

这样就可以让链接在文本中显示。然而，你也可以控制当链接被点击的时候会发生什么，实现这个可以使用UITextViewDelegate协议的新的shouldInteractWithURL方法，就像这样：

- (BOOL)textView:(UITextView *)textView shouldInteractWithURL:(NSURL *)URL inRange:(NSRange)characterRange {
    if ([[URL scheme] isEqualToString:@"username"]) {
        NSString *username = [URL host];
        // do something with this username
        // ...
        return NO;
    }
    return YES; // let the system open this URL
}