Aura Action javascript object has setCallback function that we use to communicate with the server. The first parameter of the function is scope. Aura documentation has the following explanation:
Scope : Object
The scope in which the function is executed. You almost always want to set scope to the keyword this.
Experimenting with this keyword inside the component results in undefined when used inside controller.js and the helper object instance when used inside helper.js. Does someone know what the scope parameter is affecting? Using this feels wrong as it can be almost anything depending on the place in code the setCallback is executed from.
P.S. currently I have problems with private attribute visibility inside the action callback function so I am trying to eliminate all possible causes.