(Swift 3,4,5...) Download Object from Google Cloud Storage

Demonstrates how to download an object from Google Cloud Storage to a file.

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

func chilkatTest() {
    // This example 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 
    // scope "https://www.googleapis.com/auth/cloud-platform"

    // In this example, Get Google Cloud Storage OAuth2 Access Token, 
    // the service account access token was saved to a text file.  This example fetches the access token from the file..
    let sbToken = CkoStringBuilder()!
    sbToken.loadFile("qa_data/tokens/googleCloudStorageAccessToken.txt", charset: "utf-8")

    // Send a GET equivalent to this curl command.

    // curl -X GET \
    //     -H "Authorization: Bearer [OAUTH2_TOKEN]" \
    //     -o "[SAVE_TO_LOCATION]" \
    //     "https://www.googleapis.com/storage/v1/b/[BUCKET_NAME]/o/[OBJECT_NAME]?alt=media"

    let http = CkoHttp()!

    http.authToken = sbToken.getAsString()

    // Construct a URL to download an object named "starfish.jpg" from the "chilkat-ocean" bucket.
    http.setUrlVar("bucket_name", value: "chilkat-ocean")
    http.setUrlVar("object_name", value: "starfish.jpg")
    var url: String? = "https://www.googleapis.com/storage/v1/b/{$bucket_name}/o/{$object_name}?alt=media"

    // If there is an error response, then we didn't actually download the file data,
    // but instead we downloaded an error response..
    let fileData = CkoBinData()!
    var success: Bool = http.downloadBd(url, binData: fileData)
    if success == false {
        print("\(http.lastErrorText!)")
        return
    }

    let sbErrorResponse = CkoStringBuilder()!
    var responseCode: Int = http.lastStatus.intValue
    if responseCode == 401 {
        print("If invalid credentials, then it is likely the access token expired.")
        print("Your app should automatically fetch a new access token and re-try.")
    }

    if responseCode != 200 {
        // Get the error response
        sbErrorResponse.appendBd(fileData, charset: "utf-8", offset: 0, numBytes: 0)
        print("Error response code = \(responseCode)")
        print("Error:")
        print("\(sbErrorResponse.getAsString()!)")
        return
    }

    print("Success.")

    // Save the downloaded data to a file.
    success = fileData.writeFile("qa_output/starfish.jpg")

}