Get the class deal with the cache expiration

Basically, I think it would be simpler to let the class deal with the cache expiration. That way, you just have to call "get_data()" outside the class and it would return either the cached version or the new version of the data if the cache expired.

Something along these lines in the class:
In googleWeather class:

  public function get_data(){
    // Get the data from the cache if available and not expired, else build it
    $cache = $this->get_cache();
    return $cache == FALSE ? $this->build_data() : $cache;
  }

  /**
   * Get a cached version of the data.
   * If the version has expired, return FALSE.
   */
  private function get_cache(){
    $cache_id = $this->weather_get_cache_id();

    // Return cache if possible, and if expiration time is still more than current time.
    $cache = cache_get($cache_id, 'cache_block');
    if (!empty($cache) && isset($cache->data) && ($cache->expire > time())) {
      return $cache->data;
    }

    return FALSE;
  }

  /**
   * Store a cached version of the data.
   */
  private function set_cache($data){
    $cache_id = $this->weather_get_cache_id();
    $expired_time = time() + variable_get('google_weather_block_cache', 3600);
    cache_set($cache_id , $data, 'cache_block', $expired_time);
  }

  private function build_data(){
    // the usual stuff to retrieve the data from Google Weather
	...
	
	// Cache the new generated data
    $this->set_cache($data);

    return $data;
 }

  /**
   * Helper function to retrieve cache id.
   */
  private function weather_get_cache_id(){
    $id = isset($this->location->bid) ? "bid_" . $this->location->bid : "uid_" . $this->location->uid;

    return 'google_weather_' . $id;
  }

In google_weather.module:

/**
 * Build the markup for the data retrieved from Google Weather.
 */
function google_weather_show($bid) {
  $location = location_load($bid);
  $weather = new googleWeather($location);
  $content = theme('google_weather_block', $weather->get_data());

  return array('#markup' => $content);
}