Question

这是我对UICollectionUICollectionViewControllerView

的覆盖函数

override func collectionView(collectionView: UICollectionView, viewForSupplementaryElementOfKind kind: String, atIndexPath indexPath: NSIndexPath) -> UICollectionReusableView {
        var view =  UICollectionReusableView()
        if kind == UICollectionElementKindSectionHeader {
            let viewHeader : Header = collectionView.dequeueReusableSupplementaryViewOfKind(kind, withReuseIdentifier: "header", forIndexPath: indexPath) as! Header
            if let userName = viewHeader.userName {
                userName.text = "James Bond"
            }

            view = viewHeader
        }

        return view

    }

问题是每当我尝试运行应用程序时，在调试之后它总是弹出错误＆＃34;致命错误：在展开可选值时意外发现nil＆＃34;在行

let viewHeader : Header = collectionView.dequeueReusableSupplementaryViewOfKind(kind, withReuseIdentifier: "header", forIndexPath: indexPath) as! Header

以下是我的viewDidLoad覆盖

override func viewDidLoad() {
super.viewDidLoad()

let layout = UICollectionViewFlowLayout()

collectionView = UICollectionView(frame: self.view.frame, collectionViewLayout: layout)
self.collectionView!.delegate = self
collectionView!.dataSource = self

collectionView!.registerClass(SquareCell.self, forCellWithReuseIdentifier: "cell")
collectionView!.registerClass(Header.self, forSupplementaryViewOfKind: UICollectionElementKindSectionHeader, withReuseIdentifier: "header")  // UICollectionReusableView
layout.headerReferenceSize = CGSizeMake(self.view.frame.width, 200)

let cellNib = UINib(nibName: "SquareCell", bundle: nil)
collectionView!.registerNib(cellNib, forCellWithReuseIdentifier: "cell")

let headerlNib = UINib(nibName: "HeaderView", bundle: nil)
collectionView!.registerNib(headerlNib, forCellWithReuseIdentifier: "header")


self.view.addSubview(collectionView!)

}

Answer 1

我发现在我的Header.swift类中，我不小心添加了不存在的图像名称

module PgTags

  def tags=(value)
    write_attribute :tags, value.uniq
  end

end

class Rule < ActiveRecord::Base
  include PgTags
end

r = Rule.new
r.tags = %w(one two one)
puts r.tags # outputs ['one', 'two']
r.tags << 'one'
puts r.tags # should still output ['one', 'two']

所以我删除了图片名称，所有这些都恢复正常：）

自定义标题＆＃34;致命错误：在展开可选值时意外发现nil＆＃34;

1 个答案: