excel - GET 请求数据不更新

Question

我正在尝试从 API 检索数据，但即使我在 GET 请求之前将其设置为空，我的变量也不会更新。

只有当我关闭 Excel 并重新打开它时，变量的数据才会更新。

有什么解释吗？我已经挠头这么久了。

这是代码

Sub getJsonResult()
    Dim objRequestt As Object
    Dim strUrl As String
    Dim blnAsync As Boolean
    Dim strUrlXBTUSD As String
    Dim strResponse As String
    Dim jsonText As String
    Dim jsonObject As Object, item As Object
    Dim i As Integer

    'setting up the variable to 0 or nothing

    strUrlXBTUSD = ""
    strResponsee = ""
    jsonText = ""
    i = 0
 blnAsync = False
 Set item = Nothing
 Set jsonObject = Nothing
 Set objRequestt = Nothing
 Set objRequestt = CreateObject("MSXML2.XMLHTTP")
    strUrlXBTUSD = "https://www.bitmex.com/api/v1/orderBook/L2?symbol=XBTUSD&depth=3"
    blnAsync = True


    'Starting the GET request

    ThisWorkbook.Activate
    With objRequestt
        .Open "GET", strUrlXBTUSD, blnAsync
        .SetRequestHeader "Content-Type", "application/json"
        .send
        strResponse = .responseText 'here the response is always the same except if i Close Excel
           Debug.Print strResponsee
    End With
End Sub

最后，即使经过几次 F5 刷新，“strResponse”也始终相同。我可以看到数据在网络浏览器上不再准确。我希望 VBA 程序在不关闭 Excel 的情况下获取准确的数据并刷新。

怎么做？

Answer 1

您可以添加一条指令以避免提供缓存结果(服务器可以忽略这一点，但我过去在这方面取得了很好的成功)。确保您的 async 参数始终为 False，并在测试之间留出更多时间。我注意到有时价格变化缓慢，因此您可能会由于间隔太小/尝试次数不足而错过变化。您会注意到 size虽然改变。您应该添加 max timeout到底部脚本中的循环。

还删除了匈牙利符号。

Option Explicit

Public Sub getJsonResult()
    Dim http As Object
    Dim urlXBTUSD As String
    Dim response As String
    Dim j As Long
    Const ASYNC_ARG As Boolean = False

    Set http  = CreateObject("MSXML2.XMLHTTP")
    For j = 1 To 10
        response = vbNullString
        urlXBTUSD = "https://www.bitmex.com/api/v1/orderBook/L2?symbol=XBTUSD&depth=3"

        With http 
            .Open "GET", urlXBTUSD,  ASYNC_ARG
            .setRequestHeader "Content-Type", "application/json"
            .setRequestHeader "If-Modified-Since", "Sat, 1 Jan 2000 00:00:00 GMT"
            .send
            response = .responseText
            Debug.Print response
        End With
        Application.Wait Now + TimeSerial(0, 0, 15)
    Next
End Sub

这是一个漫长而乏味的证明方法，通过循环直到退货集合中第一个项目的价格发生变化。我用 jsonconverter.bas添加到项目和 VBE > 工具 > 引用 > Microsoft 脚本运行时引用。

Option Explicit

Public Sub getJsonResult()
    Dim http  As Object
    Dim urlXBTUSD As String
    Dim response As String
    Dim j As Long
    Const ASYNC_ARG As Boolean = False
    Dim price As String, firstValue As String

    Set http  = CreateObject("MSXML2.XMLHTTP")
    urlXBTUSD = "https://www.bitmex.com/api/v1/orderBook/L2?symbol=XBTUSD&depth=3"

    With http 
        .Open "GET", urlXBTUSD,  ASYNC_ARG
        .setRequestHeader "Content-Type", "application/json"
        .setRequestHeader "If-Modified-Since", "Sat, 1 Jan 2000 00:00:00 GMT"
        .send
         firstValue = JsonConverter.ParseJson(.responseText)(1)("price")
        Debug.Print  firstValue
        Do
            .Open "GET", urlXBTUSD, blnAsync
            .setRequestHeader "Content-Type", "application/json"
            .setRequestHeader "If-Modified-Since", "Sat, 1 Jan 2000 00:00:00 GMT"
            .send
            price = JsonConverter.ParseJson(.responseText)(1)("price")
            Application.Wait Now + TimeSerial(0, 0, 5)
        Loop While price = firstValue
        Debug.Print price
    End With
End Sub