I stumble upon scala code like this:
var folderName: String = _
What does the = _ do? And is there a proper name for this language feature? 
I stumble upon scala code like this:
var folderName: String = _
What does the = _ do? And is there a proper name for this language feature? 
 
    
    = _ is used to set the default value when initialising a variable.
var s: String = _ will set s equal to null.var i: Int = _ will set i equal to 0.