(C++) Xero Download Attachment for an Item (such as an Invoice)

Demonstrates how to download a particular attachment for a particular Xero item.

For more information, see https://developer.xero.com/documentation/api/attachments#GET

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#include <CkHttp.h>
#include <CkJsonObject.h>
#include <CkBinData.h>

void ChilkatSample(void)
    {
    // This example requires the Chilkat API to have been previously unlocked.
    // See Global Unlock Sample for sample code.

    CkHttp http;

    CkJsonObject jsonToken;
    bool success = jsonToken.LoadFile("qa_data/tokens/xero-access-token.json");
    if (success == false) {
        std::cout << jsonToken.lastErrorText() << "\r\n";
        return;
    }

    http.put_AuthToken(jsonToken.stringOf("access_token"));

    // Replace the value here with an actual tenant ID obtained from this example:
    // Get Xero Tenant IDs
    http.SetRequestHeader("Xero-tenant-id","83299b9e-5747-4a14-a18a-a6c94f824eb7");

    http.put_Accept("application/json");

    // The example to list Xero attachments shows how to get attachment information.
    // Here's a sample JSON response obtained form listing attachments:
    // Your application can get the AttachmentID's and filenames from it.

    // {
    //   "Id": "24bfbcb9-dec9-4d33-835c-8f165d776766",
    //   "Status": "OK",
    //   "ProviderName": "Chilkat2222",
    //   "DateTimeUTC": "\/Date(1587213296972)\/",
    //   "Attachments": [
    //     {
    //       "AttachmentID": "daf106e2-8634-4349-bfcc-86c1df0793b2",
    //       "FileName": "penguins.jpg",
    //       "Url": "https://api.xero.com/api.xro/2.0/Invoices/0032f627-3156-4d30-9b1c-4d3b994dc921/Attachments/penguins.jpg",
    //       "MimeType": "image/jpg",
    //       "ContentLength": 777835
    //     }
    //   ]
    // }

    const char *url = "https://api.xero.com/api.xro/2.0/{$Endpoint}/{$Guid}/Attachments/{$AttachmentId}";

    // Endpoint can be Invoices, Receipts, CreditNotes, PurchaseOrders, etc.
    http.SetUrlVar("Endpoint","Invoices");

    // Guid is the ID of the item, such as the InvoiceID.
    http.SetUrlVar("Guid","0032f627-3156-4d30-9b1c-4d3b994dc921");

    // AttachmentId is the ID of the particular attachment to be downloaded
    http.SetUrlVar("AttachmentId","daf106e2-8634-4349-bfcc-86c1df0793b2");

    // Download the attachment data into bd.
    CkBinData bd;
    success = http.QuickGetBd(url,bd);
    if (success == false) {
        std::cout << http.lastErrorText() << "\r\n";
        return;
    }

    std::cout << "Response Status Code: " << http.get_LastStatus() << "\r\n";

    if (http.get_LastStatus() == 200) {
        // Success
        // Save to a file..
        success = bd.WriteFile("qa_output/penguines.jpg");
    }
    else {
        // Failed.  bd contains error information..
        std::cout << bd.getString("utf-8") << "\r\n";
    }
    }