swift - swift中从外部函数调用值变量

Question

我在从外部函数调用类中的变量时遇到问题。

Swift 给出以下错误:使用未解析的标识符“imageFilename” 我怎样才能解决它？我应该如何获取Filename变量的值？

我的代码:

func collectionView(collectionView: UICollectionView, cellForItemAtIndexPath indexPath: NSIndexPath) -> UICollectionViewCell {

    if (collectionView == self.collectionView1)
    {
        let cell : FeaturedCollectionViewCell = collectionView.dequeueReusableCellWithReuseIdentifier(self.reuseIdentifierFeatured, forIndexPath: indexPath) as! FeaturedCollectionViewCell

        let imgURL: NSURL = NSURL(string: "http://localhost:9001/feature-0.jpg")!
        let request: NSURLRequest = NSURLRequest(URL: imgURL)

        let session = NSURLSession.sharedSession()
        let task = session.dataTaskWithRequest(request){
            (data, response, error) -> Void in

            if (error == nil && data != nil)
            {
                func display_image()
                {
                   let imageFilename = UIImage(data: data!)
                }
                dispatch_async(dispatch_get_main_queue(), display_image)
            }
        }

        task.resume()

        cell.featuredImage.image = UIImage(named: imageFilename)
        return cell
    }
}

Image capture link

Answer 1

如果您在函数外部声明变量并在函数内部设置值，怎么样？然后您就可以访问该变量及其值。

您的问题肯定是您无法访问该变量，因为它只是在函数内部知道。

代码:

像这样尝试一下...

func collectionView(collectionView: UICollectionView, cellForItemAtIndexPath indexPath: NSIndexPath) -> UICollectionViewCell {



if (collectionView == self.collectionView1)
{
    let cell : FeaturedCollectionViewCell = collectionView.dequeueReusableCellWithReuseIdentifier(self.reuseIdentifierFeatured, forIndexPath: indexPath) as! FeaturedCollectionViewCell

    var imageFilename: UIImage


    let imgURL: NSURL = NSURL(string: "http://localhost:9001/feature-0.jpg")!
    let request: NSURLRequest = NSURLRequest(URL: imgURL)

    let session = NSURLSession.sharedSession()
    let task = session.dataTaskWithRequest(request){
        (data, response, error) -> Void in




        if (error == nil && data != nil)
        {
            func display_image()
            {
               imageFilename = UIImage(data: data!)
            }

            dispatch_async(dispatch_get_main_queue(), display_image)
        }


    }

    task.resume()

    cell.featuredImage.image = UIImage(named: imageFilename)
    return cell
}
}

如果这对您有用，请给我写信。