Using the google-api-ruby-client gem, here is an example for fetching Google Analytics Reporting API V4 data.

example.rb

require 'google/apis/analyticsreporting_v4'

analytics = Google::Apis::AnalyticsreportingV4::AnalyticsReportingService.new

# Authentication / Authorization
# via credentials.json
#
# File downloaded via Google's API Manager
# - Create a Service Account
# - Add the service account's email address to your Google Analytics account
# - Download and save json credentials locally
#
credentials = Google::Auth::ServiceAccountCredentials.make_creds(json_key_io: IO.new(IO.sysopen('credentials.json')))
credentials.scope = 'https://www.googleapis.com/auth/analytics.readonly'
analytics.authorization = credentials.fetch_access_token!({})["access_token"]

request = {
  report_requests:[
    {
      metric:[
        {
          expession: "ga:totalEvents"
        }
      ],
      dimensions:[
        { name:"ga:eventCategory" },
        { name: "ga:eventAction" },
        { name:"ga:eventLabel" },
        { name: "ga:deviceCategory" }
      ],
      dimension_filter_clauses:[
        {
          operator: "AND", # Default is 'OR'
          filters: [
            {
              dimension_name: "ga:eventCategory",
              operator: "EXACT",
              expressions: ["Links"] # Filter to Links
            },
            {
              dimension_name: "ga:eventLabel",
              operator: "REGEXP",
              expressions: ["hostname"] # Filter label values
            },
          ]
        }
      ],
      date_ranges:[
        {
          start_date: "2017-01-01",
          end_date: "2017-01-02"
        }
      ],
      view_id:"ga:XXXXXX" # Find your own view
}]}

results = analytics.batch_get_reports Google::Apis::AnalyticsreportingV4::GetReportsRequest.new(request)

pp results