Swift - NSURL错误 [英] Swift - NSURL error

问题描述

尝试使用下面的 NSURL 类时出错，下面的代码实际上是试图将我从Facebook拉入的图像存储到 ImageView的。错误如下：

Getting an error when trying to use the NSURL class below, the code below is essentially trying to store an image I am pulling in from Facebook into an imageView. The error is as follows:

value of optional type 'NSURL?' not unwrapped, did you mean to use '!' or '?' 

不确定为什么会发生这种情况，帮助！

Not sure why this is is happening, help!

import UIKit

class ViewController: UIViewController {

    @IBOutlet weak var myImage: UIImageView!

    override func viewDidLoad() {

        super.viewDidLoad()

        let myProfilePictureURL = NSURL(string: "http://graph.facebook.com/bobdylan/picture")
        let imageData = NSData(contentsOfURL: myProfilePictureURL)
        self.myImage.image = UIImage(data: imageData)
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }
}

推荐答案

你正在调用的 NSURL 构造函数有这个签名：

The NSURL constructor you're calling has got this signature:

convenience init?(string URLString: String)

？表示构造函数可能不返回值，因此它被认为是可选。

? means that the constructor may not return a value, hence it is considered as an optional.

NSData 构造函数也是如此：

init?(contentsOfURL url: NSURL)

快速解决方法是：

let myProfilePictureURL = NSURL(string: "http://graph.facebook.com/bobdylan/picture")
let imageData = NSData(contentsOfURL: myProfilePictureURL!)
self.myImage.image = UIImage(data: imageData!)

最好的解决方案是检查（解包）这些选项，即使你确定它们包含一个值！

The best solution is to check (unwrap) those optionals, even if you're sure that they contain a value!

您可以在optiona上找到更多信息在这里：链接到Apple官方文档。

You can find more infos on optionals here: link to official Apple documentation.

这篇关于Swift - NSURL错误的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！