如何从Swift中的Closure返回值？(How to return value from a Closure in Swift?)

 所以我在我的应用程序中使用了fabric插件/ Twitter-kit来使用twitter API。 我想获取名人个人资料图片的图片网址。 这里是我的代码如下。 
 
func getImageURL(celebrity :String) -> String{

    var imageURL = ""
    let client = TWTRAPIClient()
    let statusesShowEndpoint = userSearch
    let params = ["q": celebrity,
                  "page" : "1",
                  "count" : "1"
                  ]
    var clientError : NSError?

    let request = client.URLRequestWithMethod("GET", URL: statusesShowEndpoint, parameters: params, error: &clientError)

     client.sendTwitterRequest(request) { (response, data, connectionError) -> Void in
        if connectionError != nil {
            print("Error: \(connectionError)")
        }

        do {
            let json = try NSJSONSerialization.JSONObjectWithData(data!, options: [])
            print("json: \(json)")

            let profileImageURL: String? = json[0].valueForKey("profile_image_url_https") as? String

            imageURL =  self.cropTheUrlOfImage(profileImageURL!)
            print(imageURL)

            //how do i return the value back. confused ?????
            return imageURL

        } catch let jsonError as NSError {
            print("json error: \(jsonError.localizedDescription)")
        }
    }

    return imageURL

}
 
 我不知道如何返回值，因为方法在闭包完全执行之前完成。 我是新来的迅速，任何帮助表示赞赏。 
 
 我想在tableview的cellForRowIndexPath中使用这个方法来下载imageURl中的图像。 

So I am using fabric plugin/Twitter-kit to use twitter api in my application. I want to get the image URL of profile picture of a celebrity. here is my code below.
 
func getImageURL(celebrity :String) -> String{

    var imageURL = ""
    let client = TWTRAPIClient()
    let statusesShowEndpoint = userSearch
    let params = ["q": celebrity,
                  "page" : "1",
                  "count" : "1"
                  ]
    var clientError : NSError?

    let request = client.URLRequestWithMethod("GET", URL: statusesShowEndpoint, parameters: params, error: &clientError)

     client.sendTwitterRequest(request) { (response, data, connectionError) -> Void in
        if connectionError != nil {
            print("Error: \(connectionError)")
        }

        do {
            let json = try NSJSONSerialization.JSONObjectWithData(data!, options: [])
            print("json: \(json)")

            let profileImageURL: String? = json[0].valueForKey("profile_image_url_https") as? String

            imageURL =  self.cropTheUrlOfImage(profileImageURL!)
            print(imageURL)

            //how do i return the value back. confused ?????
            return imageURL

        } catch let jsonError as NSError {
            print("json error: \(jsonError.localizedDescription)")
        }
    }

    return imageURL

}
 
I don't know how to return value because the method finishes before the closure executes completely. I am new to swift, Any help is appreciated.
 
I want to use this method in cellForRowIndexPath in tableview to dowload image from imageURl.

原文：https://stackoverflow.com/questions/38296910