變量，因爲你想<code>print(d)</code>外完成塊的網絡呼叫

Question

我variavle d後未分配將返回nil

var d: Int! 

Alamofire.request(mapsUrl).responseJSON(completionHandler: { (response) in 
     let jsonObject = JSON(response.result.value) 
     let value = jsonObject["rows"][0]["elements"][0]["distance"]["value"].int 

     var converted = 0 
     if value! <= 5000{ 
      converted = (value!/1000) * 80 
     }else{ 
      converted = (value!/1000) * 65 
     } 
     if converted < 400{ 
      converted = 400 
     }else if converted == 0{ 
      converted = 400 
     } 
     d = converted 
    }) 
print(d) 

但d將返回零

Answer 1

，該聲明將之前執行您的網絡請求已完成。嘗試把該完成塊內：

Alamofire.request(mapsUrl).responseJSON(completionHandler: { (response) in 
    let jsonObject = JSON(response.result.value) 
    let value = jsonObject["rows"][0]["elements"][0]["distance"]["value"].int 

    var converted = 0 
    if value! <= 5000{ 
     converted = (value!/1000) * 80 
    }else{ 
     converted = (value!/1000) * 65 
    } 
    if converted < 400{ 
     converted = 400 
    }else if converted == 0{ 
     converted = 400 
    } 
    d = converted 
    print(d) 
})