模糊使用函数错误

Question

我使用以下代码

@IBOutlet weak var hashtagableTextView: UITextView!

在viewDidload方法中：

let hashtagableDelegate = HashtagableTextInputDelegate(textView: hashtagableTextView, userDelegate: self)

hashtagableDelegate.didStartTypingHashtag = { partialHashtag in
    let searchableString = partialHashtag.replacingOccurrences(of: "#", with: "")
    hashtagableDelegate.showSuggestedHashtags(hashtagDatabase.filter({ $0.lowercased().contains(searchableString.lowercased()) }))
}

hashtagableTextView.delegate = hashtagableDelegate

我收到错误

  

模糊地使用contains

我该如何解决？