Swift3 使用未解析标识符'；contentURL'；

我得到了这个错误：

shareButton.shareContent = FBSDKShareLinkContent(contentURL:contentURL,
contentTitle: "My Share Title", 
contentDescription: "Lorem ipsum dolor sit amet.", 
imageURL: imageURL, 
peopleIDs: ["1561082740838259"], 
placeID: "166793820034304", 
ref: "myRefId")

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您必须像

imageURL

那样创建

contentURL

：

let contentURL = NSURL(string: "https://www.facebook.com/FacebookDevelopers") 
let content = FBSDKShareLinkContent()
content.contentURL = contentURL
...

let imageURL = NSURL(string: "http://upload.wikimedia.org/wikipedia/commons/thumb/9/95/Facebook_Headquarters_Menlo_Park.jpg/2880px-Facebook_Headquarters_Menlo_Park.jpg")
shareButton.shareContent = FBSDKShareLinkContent(contentURL:contentURL, contentTitle ...

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第二个

contentURL

来自哪里？这就是编译器想要知道的？我在下面提到了我的全部代码。请检查一下