How to use reduce or fold to avoid mutable state

Question

I have a mutable variable in my code that I want to avoid by using some of aggregation function. Unfortunatelly I couldn't find solution for the following pseudocode.

    def someMethods(someArgs) = {
      var someMutableVariable = factory

      val resources = getResourcesForVariable(someMutableVariable)
        resources foreach (resource => {
            val localTempVariable = getSomeOtherVariable(resource)
            someMutableVariable = chooseBetteVariable(someMutableVariable, localTempVariable)
        })

        someMutableVariable
    }

I have two places in my code where I need to build some variable, then in loop compare it with other possibilities and if it worse then replace it with this newly possibility.

Answer 1

If you resources variable supports it:

 //This is the "currently best" and "next" in list being folded over
 resources.foldLeft(factory)((cur, next) => 
   val local = getSomeOther(next)

   //Since this function returns the "best" between the two, you're solid
   chooseBetter(local, cur) 
 }

and then you don't have mutable state.