(Swift 3,4,5...) Download Binary File to In-Memory Bytes

This example demonstrates how to download the binary content of a file from Google Drive directly into local memory.

Chilkat Downloads for the Swift Programming Language MAC OS X (Cocoa) Objective-C/Swift Libs iOS Objective-C/Swift Libs

func chilkatTest() {
    var success: Bool = true

    // It requires the Chilkat API to have been previously unlocked.
    // See Global Unlock Sample for sample code.

    // This example uses a previously obtained access token having permission for the 
    // Google Drive scope.

    let gAuth = CkoAuthGoogle()!
    gAuth.accessToken = "GOOGLE-DRIVE-ACCESS-TOKEN"

    let rest = CkoRest()!

    // Connect using TLS.
    // A single REST object, once connected, can be used for many Google Drive REST API calls.
    // The auto-reconnect indicates that if the already-established HTTPS connection is closed,
    // then it will be automatically re-established as needed.
    var bAutoReconnect: Bool = true
    success = rest.connect("www.googleapis.com", port: 443, tls: true, autoReconnect: bAutoReconnect)

    // Provide the authentication credentials (i.e. the access token)
    rest.setAuthGoogle(gAuth)

    // ------------------------------------------------------------------------------
    // To download a file, we must know the file ID.
    // In a previous example (see Build Local Metadata Cache
    // we built a local cache to make it easy to lookup file IDs given a file path.
    // Let's say we want to download "testFolder/abc/123/penguins.jpg".
    // First we lookup the fileId in the cache.  With the fileId, we can download the file.
    let gdCache = CkoCache()!
    gdCache.level = 0
    gdCache.addRoot("C:/ckCache/googleDrive")

    var fileId: String? = gdCache.fetchText("testFolder/abc/123/penguins.jpg")
    if gdCache.lastMethodSuccess != true {
        print("Filepath not found in cache.")
        return
    }

    // We need to send a GET request like this:
    // GET https://www.googleapis.com/drive/v3/files/fileId?alt=media
    // The fileId is part of the path.
    let sbPath = CkoStringBuilder()!
    sbPath.append("/drive/v3/files/")
    sbPath.append(fileId)
    rest.addQueryParam("alt", value: "media")

    // To download to memory, we'll send the request in one call, then receive
    // the response header, and then the response body.
    // If the response header indicates failure or an unexpected response, then the
    // body is not the data we desire.

    // First send the HTTP request.
    success = rest.sendReqNoBody("GET", uriPath: sbPath.getAsString())
    if success != true {
        print("\(rest.lastErrorText!)")
        return
    }

    // Get the response header.
    var statusCode: Int = rest.readResponseHeader().intValue
    if statusCode != 200 {
        print("response status code = \(rest.responseStatusCode.intValue)")
        print("response status text = \(rest.responseStatusText!)")
        print("response header: \(rest.responseHeader!)")

        // Read the response body (which should be error text or HTML)
        var errResponseBody: String? = rest.readRespBodyString()
        if rest.lastMethodSuccess == true {
            print("response body: \(errResponseBody!)")
        }

        return
    }

    // Read the response body, which should contain the file data.
    var jpgBytes: NSData
    jpgBytes = rest.readRespBodyBinary()
    if rest.lastMethodSuccess != true {
        print("\(rest.lastErrorText!)")
        return
    }

    // Save jpgBytes to a file so we can examine the file to verify that it worked.
    let fac = CkoFileAccess()!
    fac.writeEntireFile("qa_output/penguins_out.jpg", fileData: jpgBytes)

    print("File downloaded.")

}