How to answer "why scala provides `object` keyword"? -



How to answer "why scala provides `object` keyword"? -

this question has reply here:

why singleton objects more object-oriented? 7 answers

someone asked me: why scala provides object keyword?

i reply object can:

create single instance on language level create new instance of other types factories combine different traits

but said "these object can do, not why".

what should reply question?

(i read articles object, can answer: because scala want back upwards module on language level? )

object there avoid static members. scala designed pure object oriented language, , static isn't object oriented. static makes code harder understand mix code doesn't belong conceptually. in general, separating static , instance members idea.

also object reduces boilerplate implementing singleton pattern , makes useless types less present.

just compare:

class someglobalservice { private someglobalservice instance = null private someglobalservice() { <constructor code> } public static someglobalservice getinstance() { if (instance == null) instance = new someglobalservice homecoming instance } <members> } someglobalservice.getinstance().<somemember>

to

object someglobalservice { <constructor code> <members> } someglobalservice.<somemember>

in first illustration bundle polluted useless class someglobalservice defenetely never utilize directly. in scala type less visible someglobalservice.type.

scala object module

Comments

Post a Comment

Popular posts from this blog

ruby on rails - Devise Logout Error in RoR -

ruby on rails - Devise Logout Error in RoR - while using devise in ror, encountering unusual error when trying log out url different root url. displays me : actioncontroller::invalidauthenticitytoken in devise::sessionscontroller#destroy" for illustration if rooting path after log in '/structure', , seek log out '/general' error, while logging out '/structure' fine. any help highly appreciated. ruby-on-rails ruby devise
Read more

c# - Create a Notification Object (Email or Page) At Run Time -- Dependency Injection or Factory -

c# - Create a Notification Object (Email or Page) At Run Time -- Dependency Injection or Factory - i have code emails me notification when happens. trying add together page , also remove dependency on email. for reference; have name of notification want send stored string in database. @ runtime have list of people , string representation of want receive. i thought dependency injection ninject, kernel bindings got big , seemed hacking together. then thought simple factory, activator.createinstance(email/page) inotifcation, don't know how handle differing constructor parameters (unless utilize common, complex property, employee, has info need). so far have this: public interface inotification { void sendmessage(); } public class email: inotification { private readonly string _toemailaddress; private string body { { homecoming "email"; } } private static string smtphost { ...
Read more

model view controller - MVC Rails Planning -

model view controller - MVC Rails Planning - i'm starting rails , i'm building app stores films info, user can watch film , give grade on web application. i have coded cinema model, controller , views. now, have 2 questions: should need create model , controller grading? in case, should create or should wait , create first users model , controller? yes, on model , controller grades. that'd feasible way maintain track of who's graded what. it's create first, i'd start users, since grades depend on both films , users. ruby-on-rails model-view-controller
Read more