gweather | full stack app that gives you realtime weather updates | GraphQL library

According to the error message, gweather_location_get_city_name () is emitting an error because the location is NULL (loc != NULL is false). Look at where you're calling get_city_name (). It's at the very top of your constructor, before location is set to anything. You need to wait until you have a location before you try to use it.

Then you should use something like the Nimbus code. It handles the case when simple.get_location () returns NULL (if it can't find your location), and also initializes the GWeather location so it can call find_nearest_city ().