(Swift) Google Sheets Refresh an Expired Access Token

Demonstrates how to refresh an expired access token. If a Google Sheets REST API call results in a 401 "unauthorized" response, then it is likely the access token expired. An application should be able to automatically refresh the access token with no user interaction and then re-try the request with the newly obtained access token.

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.

    //  It is assumed we previously obtained an OAuth2 access token.
    //  This example loads the JSON access token file
    //  saved by this example: Get Google Sheets OAuth2 Access Token

    let jsonToken = CkoJsonObject()
    var success: Bool = jsonToken.LoadFile("qa_data/tokens/googleSheets.json")
    if success != true {
        print("Failed to load googleSheets.json")
        return
    }

    //  The access token JSON looks like this:

    //  	{
    //  	 "access_token": "abac.Ci-ZabcdF37-NUrmSzxbHxTsMbtlN-uPfabcdAQN_2ekzj0s5ofCzRabcdTDMGaa2Q",
    //  	 "token_type": "Bearer",
    //  	 "expires_in": 3600,
    //  	 "refresh_token": "1/lEe5abcdNJ77eOSDBabcdkQGVmDalkwabcdR2Hatbo"
    //  	}
    // 

    let oauth2 = CkoOAuth2()

    oauth2.TokenEndpoint = "https://www.googleapis.com/oauth2/v4/token"

    //  Replace these with actual values.
    oauth2.ClientId = "GOOGLE-CLIENT-ID"
    oauth2.ClientSecret = "GOOGLE-CLIENT-SECRET"

    //  Get the "refresh_token"
    oauth2.RefreshToken = jsonToken.StringOf("refresh_token")

    //  Send the HTTP POST to refresh the access token..
    success = oauth2.RefreshAccessToken()
    if success != true {
        print("\(oauth2.LastErrorText)")
        return
    }

    //  The response contains a new access token, but we must keep
    //  our existing refresh token for when we need to refresh again in the future.
    jsonToken.UpdateString("access_token", value: oauth2.AccessToken)

    //  Save the new JSON access token response to a file.
    let sbJson = CkoStringBuilder()
    jsonToken.EmitCompact = false
    jsonToken.EmitSb(sbJson)
    sbJson.WriteFile("qa_data/tokens/googleSheets.json", charset: "utf-8", emitBom: false)

    print("OAuth2 authorization granted!")
    print("New Access Token = \(oauth2.AccessToken)")

}