How do you rewrite this Scala class with variable fields in a more functional style? -

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class myclass {    var myfield = list.empty[double]   var mysecondfield = list.empty[double]    def mymethod = {      // code heavy computation      myfield = mycomputationoutput      mysecondfield = mysecondcomputationoutput   } }

i avoid saving state in myclass, seems convenient store computed values during mymethod call.

what design alternatives?

if caching results of heavy computations, use memoize pattern. compute result first time , return if parameters same:

class myclass {   var myfield = option[list[double]] = none   var mysecondfield = option[list[double]] = none    def mymethod = {     if ( ! myfield.isdefined ) {       myfield = some(mycomputationoutput)     }     if ( ! mysecondfield.isdefined ) {       mysecondfield = some(mysecondcomputationoutput)     }   } }

if values never change, consider computing them first time referenced, using lazy evaluation:

class myclass {   lazy val myfield = mycomputationoutput   lazy val mysecondfield = mysecondcomputationoutput }

another approach consider myclass 2 classes, corresponding 2 phases, i.e., before , after computation done. then, mutability global state, rather amalgam of states of 2 variables.


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