How do we use restful APIs from Excel macros (vba)?

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To use RESTful APIs from Excel macros (VBA), you can follow these general steps:

  1. Enable References:
    • Open Excel and press Alt + F11 to open the VBA editor.
    • Go to Tools > References and enable the “Microsoft XML, v6.0” or a similar reference that allows you to work with XML and HTTP requests.
  2. Create a Function for API Requests:
    • In the VBA editor, insert a new module (Insert > Module).
    • Write a function to handle the API requests. Below is a simple example using XMLHTTP:

Function GetApiResponse(apiUrl As String) As String
    Dim xmlHttp As Object
    Set xmlHttp = CreateObject("MSXML2.ServerXMLHTTP.6.0")
    
    xmlHttp.Open "GET", apiUrl, False
    xmlHttp.setRequestHeader "Content-Type", "text/xml"
    xmlHttp.send ""
    
    GetApiResponse = xmlHttp.responseText
End Function

Use the Function in Excel:

  • You can now use the GetApiResponse function in your Excel worksheet. For example:

Sub CallApi()
    Dim apiUrl As String
    Dim response As String

    ' Set your API endpoint URL
    apiUrl = "https://api.example.com/data"

    ' Call the API function
    response = GetApiResponse(apiUrl)

    ' Do something with the response, e.g., output to a cell
    Range("A1").Value = response
End Sub

Handle JSON Responses:

  • If the API returns JSON, you might want to parse it. You can use the “VBA-JSON” library for this. Download the code from GitHub and import it into your VBA project: VBA-JSON.
  • Example of parsing JSON:

Sub ParseJsonResponse()
    Dim apiUrl As String
    Dim response As String
    Dim json As Object

    ' Set your API endpoint URL
    apiUrl = "https://api.example.com/data"

    ' Call the API function
    response = GetApiResponse(apiUrl)

    ' Parse JSON response
    Set json = JsonConverter.ParseJson(response)

    ' Access data from JSON
    Dim value As String
    value = json("key")

    ' Do something with the value, e.g., output to a cell
    Range("A1").Value = value
End Sub
  1. Handle Authentication (if needed):
    • If the API requires authentication, you may need to include authentication headers in your requests. Modify the xmlHttp.setRequestHeader lines accordingly.

Keep in mind that this is a basic example, and you may need to customize it based on the specifics of the API you are working with. Additionally, some APIs might use different authentication methods (e.g., OAuth), so be sure to check the API documentation for any specific requirements.

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