如何在
swift 3中声明一个URL？
这是我尝试的代码：
var messageURL: URL = URL()
要么
var messageURL: Foundation.URL = URL()
以下是Apple的一些文档(Swift 3.0),我无法实现：
Properties whose name conflicts with Foundation types after removing their NS prefix will lead to module-qualified type names. For example,if there is a var URL: NSURL,it will be rewritten as var URL: Foundation.URL
Swift 3具有URL(一个结构体)和NSURL(一个继承自ObjC的类).情况就像String和NSString.你有两个选择：
1：如果您在声明时知道该网址：
let url = URL(string: "https://www.apple.com")
2：如果你以后只能找到这个URL：
var url: URL!
// You can check if the variable is initialized by checking it against nil:
// if url == nil { /* not initialized */ }
// When you are ready to assign it a value:
url = URL(string: "https://www.apple.com")
