As a side note of what others have explained, return
] values are used for two reasons mainly:
1. returning the value of a calculus or the result of the function called.
2. knowing if the functions has succeeded or not.
In your case both answers apply, you seem to be using global variables in your class so you don't have to return any value and both functions
] are so easy that you don't need to check their success.
You should know that main return value
] can be used to know the result of the application.
See the links to get more information.