从回调函数swift获取值

问题：我想获取ApiToken函数返回的值，以便在另一个函数中使用它。由于某些原因，我无法从该函数中获取值，它将不会返回任何内容。如何从ApiToken函数返回值并在另一个函数中使用它

下面是我的GetApiToken类和ApiToken函数 这里是我试图获取值的地方

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这是一个异步调用，因此您需要将检索到数据后发生的所有事情都放在完成回调中

func getData(_ link:String)
{
    let url = URL(string: link)!
    var request = URLRequest(url: url, 
                             cachePolicy: .reloadIgnoringCacheData,
                             timeoutInterval: 20)
    request.httpMethod = "GET"
    GetApiToken().ApiToken(link: "http://localhost:5000/auth", 
                           completionBlock: 
                           { output in
                             request.addValue("JWT  \(output)", forHTTPHeaderField: "Authorization")
                             request.setValue("application/json", forHTTPHeaderField: "Content-Type") 
                             .......
                           })

func getData(_ link:String)
    {
        let url = URL(string: link)!
        var request = URLRequest(url: url, cachePolicy: .reloadIgnoringCacheData, timeoutInterval: 20)
        request.httpMethod = "GET"
        var output = ""
        GetApiToken().ApiToken(link: "http://localhost:5000/auth", completionBlock: { str in
            output = str

        })
        request.addValue("JWT  \(output)", forHTTPHeaderField: "Authorization")
        request.setValue("application/json", forHTTPHeaderField: "Content-Type") ..........

func getData(_ link:String)
{
    let url = URL(string: link)!
    var request = URLRequest(url: url, 
                             cachePolicy: .reloadIgnoringCacheData,
                             timeoutInterval: 20)
    request.httpMethod = "GET"
    GetApiToken().ApiToken(link: "http://localhost:5000/auth", 
                           completionBlock: 
                           { output in
                             request.addValue("JWT  \(output)", forHTTPHeaderField: "Authorization")
                             request.setValue("application/json", forHTTPHeaderField: "Content-Type") 
                             .......
                           })