��权限没有,则隐藏 function forum_list_access_filter($forumlist, $gid, $allow = 'allowread') { global $grouplist; if (empty($forumlist)) return array(); if (1 == $gid) return $forumlist; $forumlist_filter = $forumlist; $group = $grouplist[$gid]; foreach ($forumlist_filter as $fid => $forum) { if (empty($forum['accesson']) && empty($group[$allow]) || !empty($forum['accesson']) && empty($forum['accesslist'][$gid][$allow])) { unset($forumlist_filter[$fid]); } unset($forumlist_filter[$fid]['accesslist']); } return $forumlist_filter; } function forum_filter_moduid($moduids) { $moduids = trim($moduids); if (empty($moduids)) return ''; $arr = explode(',', $moduids); $r = array(); foreach ($arr as $_uid) { $_uid = intval($_uid); $_user = user_read($_uid); if (empty($_user)) continue; if ($_user['gid'] > 4) continue; $r[] = $_uid; } return implode(',', $r); } function forum_safe_info($forum) { //unset($forum['moduids']); return $forum; } function forum_filter($forumlist) { foreach ($forumlist as &$val) { unset($val['brief'], $val['announcement'], $val['seo_title'], $val['seo_keywords'], $val['create_date_fmt'], $val['icon_url'], $val['modlist']); } return $forumlist; } function forum_format_url($forum) { global $conf; if (0 == $forum['category']) { // 列表URL $url = url('list-' . $forum['fid'], '', FALSE); } elseif (1 == $forum['category']) { // 频道 $url = url('category-' . $forum['fid'], '', FALSE); } elseif (2 == $forum['category']) { // 单页 $url = url('read-' . trim($forum['brief']), '', FALSE); } if ($conf['url_rewrite_on'] > 1 && $forum['well_alias']) { if (0 == $forum['category'] || 1 == $forum['category']) { $url = url($forum['well_alias'], '', FALSE); } elseif (2 == $forum['category']) { // 单页 $url = ($forum['threads'] && $forum['brief']) ? url($forum['well_alias'] . '-' . trim($forum['brief']), '', FALSE) : url($forum['well_alias'], '', FALSE); } } return $url; } function well_forum_alias() { $forumlist = forum_list_cache(); if (empty($forumlist)) return ''; $key = 'forum-alias'; static $cache = array(); if (isset($cache[$key])) return $cache[$key]; $cache[$key] = array(); foreach ($forumlist as $val) { if ($val['well_alias']) $cache[$key][$val['fid']] = $val['well_alias']; } return array_flip($cache[$key]); } function well_forum_alias_cache() { global $conf; $key = 'forum-alias-cache'; static $cache = array(); // 用静态变量只能在当前 request 生命周期缓存,跨进程需要再加一层缓存:redis/memcached/xcache/apc if (isset($cache[$key])) return $cache[$key]; if ('mysql' == $conf['cache']['type']) { $arr = well_forum_alias(); } else { $arr = cache_get($key); if (NULL === $arr) { $arr = well_forum_alias(); !empty($arr) AND cache_set($key, $arr); } } $cache[$key] = empty($arr) ? '' : $arr; return $cache[$key]; } ?>ios - NSObject proxy with weak delegate crashes with NSInvalidArgumentException unrecognized selector - Stack Overflow
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ios - NSObject proxy with weak delegate crashes with NSInvalidArgumentException unrecognized selector - Stack Overflow

programmeradmin4浏览0评论

I'm debugging a library that implements a UIScrollViewDelegate proxy (essentially) like:

class ScrollViewDelegateProxy: NSObject, UIScrollViewDelegate {
    private weak var realDelegate: UIScrollViewDelegate?

    init(scrollView: UIScrollView) {
        super.init()
        self.realDelegate = scrollView.delegate
        scrollView.delegate = self
    }

    // MARK: - UIScrollViewDelegate

    func scrollViewDidScroll(_ scrollView: UIScrollView) {
        // Do something...
        realDelegate?.scrollViewDidScroll?(scrollView)
    }

    // Other scroll delegate methods...

    // MARK: - Method Forwarding

    override func responds(to aSelector: Selector!) -> Bool {
        if let realDelegate {
            realDelegate.responds(to: aSelector)
        } else {
            super.responds(to: aSelector)
        }
    }

    override func forwardingTarget(for aSelector: Selector!) -> Any? {
        if let realDelegate, realDelegate.responds(to: aSelector) {
            realDelegate
        } else {
            super.forwardingTarget(for: aSelector)
        }
    }
}

The method forwarding is implemented in case the proxy is sent messages outside of UIScrollViewDelegate. E.g. if the scrollView were a UITableView, then the delegate property would be a UITableViewDelegate with more methods that are not supported by this proxy. In that case, it should just pass it on.

Because my use case is a UITableView. I've found that this can crash (not always) with the error message:

'NSInvalidArgumentException', reason: '-[SomeLibrary.ScrollViewDelegateProxy tableView:viewForHeaderInSection:]: unrecognized selector sent to instance'

I think this is because:

  • responds(to:) returns true for a selector while the realDelegate is in memory
  • realDelegate deallocates
  • forwardingTarget(for:) is called later with that selector, but it is not implemented on the proxy
  • The invocation causes a crash

I saw this blog post but wasn't sure what the Swift equivalent was.

Is using a weak property like this with method forwarding simply unsafe? And what might a safe implementation look like?

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