在Swift 3上运行后台线程

Question

我有一个函数是这样的：

fileprivate func setupImageViewWithURL(url: URL) {
    var image: UIImage? = nil
    do {
        try image = UIImage(data: Data(contentsOf: url))!
    } catch is NSError {
        print("Failed")
    }

    image = self.imageWithImage(sourceImage: image!, scaledToWidth: UIScreen.main.bounds.size.width)
    self.imageImageView.image = image
    self.imageImageView.frame = CGRect(x: 0, y: 0, width: UIScreen.main.bounds.size.width, height: (image?.size.height)!)
}

我想在Background thread上运行它。

我尝试过Swift2的GDC方法，但它不起作用。

Swift3中的线程主题有什么变化吗？

谢谢!

Answer 1

可以在后台加载图像，但不能在后台线程上执行UI更新。这就是函数必须包含两个线程的原因。

func setupImageViewWithURL(url: URL) {
    var image: UIImage? = nil

    DispatchQueue.global().async { 
        do {
            try image = UIImage(data: Data(contentsOf: url))!
        } catch {
            print("Failed")
        }
        DispatchQueue.main.async(execute: {
            if image != nil {
                image = self.imageWithImage(sourceImage: image!, scaledToWidth: UIScreen.main.bounds.size.width)
                self.imageImageView.image = image
                self.imageImageView.frame = CGRect(x: 0, y: 0, width: UIScreen.main.bounds.size.width, height: (image?.size.height)!)
            }
        })
    }
}

Answer 2

Swift 4.0

函数图像(url: URL) { var setupImageViewWithURL: UIImage？= nil DispatchQueue.global(qos：.background).async { do { try image = UIImage(data: Data(contentsOf: url))！} catch { print("Failed") } DispatchQueue.main.async { if image != nil { image = self.imageWithImage(sourceImage: image!，scaledToWidth: UIScreen.main.bounds.size.width) self.imageImageView.image =图像self.imageImageView.frame = CGRect(x: 0，y: 0，width: UIScreen.main.bounds.size.width，height：(image?.size.height)!) }

Answer 3

DispatchQueue.global(qos：.background).async {

}