So you’re saying flagValue = "0"; throws a null reference?
What happens if you delete that line?
And how are you making this MonoBehaviour? Is it already in place, or are you instantiating it, or are you calling .AddComponent(); ? Any other way is invalid. For instance you cannot use new
EDIT: I just noticed this is a save system. Are you relying on JSON making one of these things? That won’t work either. You must make the MonoBehaviour instance yourself (on a valid GameObject), then populate it with JSON data.
Here’s more random Load/Save steps:
Don’t use the binary formatter/serializer: it is insecure, it cannot be made secure, and it makes debugging very difficult, plus it actually will NOT prevent people from modifying your save data on their computers.
When loading, you can never re-create a MonoBehaviour or ScriptableObject instance directly from JSON. The reason is they are hybrid C# and native engine objects, and when the JSON package calls new to make one, it cannot make the native engine portion of the object.
Instead you must first create the MonoBehaviour using AddComponent() on a GameObject instance, or use ScriptableObject.CreateInstance() to make your SO, then use the appropriate JSON “populate object” call to fill in its public fields.
If you want to use PlayerPrefs to save your game, it’s always better to use a JSON-based wrapper such as this one I forked from a fellow named Brett M Johnson on github: