AngularJS When to use service instead of factory

Question

Please bear with me here  I know there are other answers such as    AngularJS  Service vs provider vs factory   However I still can t figure out when you d use service over factory   From what I can tell factory is commonly used to create  common  functions that can be called by multiple Controllers  Creating common controller functions  The Angular docs seem to prefer factory over service  They even refer to  service  when they use factory which is even more confusing  http   docs angularjs org guide dev guide services creating services  So when would one use service   Is there something that is only possible or much easier done with service   Is there anything different that goes on behind the scenes  Performance memory differences    Here s an example  Other than the method of declaration  they seem identical and I can t figure out why I d do one vs the other  http   jsfiddle net uEpkE    Update  From Thomas  answer it seems to imply that service is for simpler logic and factory for more complex logic with private methods  so I updated the fiddle code below and it seems that both are able to support private functions   myApp factory  fooFactory   function         var fooVar      var addHi   function foo   fooVar    Hi   foo         return           setFoobar  function foo               addHi foo                      getFoobar function                return fooVar                       myApp service  fooService   function         var fooVar      var addHi   function foo   fooVar    Hi   foo        this setFoobar   function foo           addHi foo             this getFoobar   function            return fooVar             function MyCtrl  scope  fooService  fooFactory        fooFactory setFoobar  fooFactory        fooService setFoobar  fooService          foobars    Hi fooFactory  Hi fooService       scope foobars             fooFactory getFoobar            fooService getFoobar

User · Answer

Even when they say that all services and factories are singleton, I don't agree 100 percent with that. I would say that factories are not singletons and this is the point of my answer. I would really think about the name that defines every component(Service/Factory), I mean:

A factory because is not a singleton, you can create as many as you want when you inject, so it works like a factory of objects. You can create a factory of an entity of your domain and work more comfortably with this objects which could be like an object of your model. When you retrieve several objects you can map them in this objects and it can act kind of another layer between the DDBB and the AngularJs model.You can add methods to the objects so you oriented to objects a little bit more your AngularJs App.

Meanwhile a service is a singleton, so we can only create 1 of a kind, maybe not create but we have only 1 instance when we inject in a controller, so a service provides more like a common service(rest calls,functionality.. ) to the controllers.

Conceptually you can think like services provide a service, factories can create multiple instances(objects) of a class

User · Answer

Can use both the way you want   whether create object or just to access functions from both       You can create new object from service   app service  carservice   function         this model   function            this name   Math random 22222           this price   1000          this colour    green           this manufacturer    bmw               controller  carcontroller   function   scope carservice          scope   new carservice model         Note      service by default returns object and not constructor function   So that s why constructor function is set to this model property  Due to this service will return object but but but inside that object will be constructor function which will be use to create new object       You can create new object from factory   app factory  carfactory   function         var model   function            this name   Math random 22222           this price   1000          this colour    green           this manufacturer    bmw             return model        controller  carcontroller   function   scope carfactory          scope   new carfactory         Note      factory by default returns constructor function and not object   So that s why new object can be created with  constructor function       Create service for just accessing simple functions   app service  carservice   function         this createCar   function             console log  createCar             this deleteCar   function             console log  deleteCar                controller  MyService   function   scope carservice         carservice createCar           Create factory for just accessing simple functions   app factory  carfactory   function          var obj               obj createCar   function                  console log  createCar                      obj deleteCar   function             console log  deleteCar                 controller  MyService   function   scope carfactory         carfactory createCar        Conclusion      you can use both the way you want whether to create new object or just to access simple functions There won t be any performance hit   using one over the other Both are singleton objects and only one instance is created per app  Being only one instance every where their reference is passed  In angular documentation factory is called service and also service is called service

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Services  Syntax  module service   serviceName   function    Result  When declaring serviceName as an injectable argument you will be provided the actual function reference passed to module service   Usage  Could be useful for sharing utility functions that are useful to invoke by simply appending    to the injected function reference  Could also be run with injectedArg call  this   or similar   Factories  Syntax  module factory   factoryName   function     Result  When declaring factoryName as an injectable argument you will be provided the value that is returned by invoking the function reference passed to module factory   Usage  Could be useful for returning a  class  function that can then be new ed to create instances   Providers  Syntax  module provider   providerName   function     Result  When declaring providerName as an injectable argument you will be provided the value that is returned by invoking the  get method of the function reference passed to module provider   Usage  Could be useful for returning a  class  function that can then be new ed to create instances but that requires some sort of configuration before being injected  Perhaps useful for classes that are reusable across projects  Still kind of hazy on this one

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allernhwkim originally posted an answer on this question linking to his blog  however a moderator deleted it  It s the only post I ve found which doesn t just tell you how to do the same thing with service  provider and factory  but also tells you what you can do with a provider that you can t with a factory  and with a factory that you can t with a service   Directly from his blog   app service  CarService   function        this dealer  Bad       this numCylinder   4       app factory  CarFactory   function         return function numCylinder          this dealer  Bad           this numCylinder   numCylinder             app provider  CarProvider   function         this dealerName    Bad       this  get   function             return function numCylinder                this numCylinder   numCylinder              this dealer   this dealerName                       this setDealerName   function str          this dealerName   str                    This shows how the CarService will always a produce a car with 4 cylinders  you can t change it for individual cars  Whereas CarFactory returns a function so you can do new CarFactory in your controller  passing in a number of cylinders specific to that car  You can t do new CarService because CarService is an object not a function   The reason factories don t work like this   app factory  CarFactory   function numCylinder          this dealer  Bad         this numCylinder   numCylinder       And automatically return a function for you to instantiate  is because then you can t do this  add things to the prototype etc    app factory  CarFactory   function         function Car numCylinder            this dealer  Bad           this numCylinder   numCylinder            Car prototype breakCylinder   function             this numCylinder -  1             return Car        See how it is literally a factory producing a car   The conclusion from his blog is pretty good      In conclusion   ---------------------------------------------------     Provider  Singleton  Instantiable   Configurable  ---------------------------------------------------     Factory   Yes        Yes            No            ---------------------------------------------------     Service   Yes        No             No            ---------------------------------------------------     Provider  Yes        Yes            Yes                  ---------------------------------------------------            Use Service when you need just a simple object such as a Hash  for   example  foo 1  bar 2  It   s easy to code  but you cannot instantiate   it    Use Factory when you need to instantiate an object  i e new   Customer    new Comment    etc    Use Provider when you need to configure it  i e  test url  QA url    production url       If you find you re just returning an object in factory you should probably use service   Don t do this   app factory  CarFactory   function         return           numCylinder  4              Use service instead   app service  CarService   function         this numCylinder   4

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Explanation  You got different things here    First     If you use a service you will get the instance of a function   this  keyword    If you use a factory you will get  the value that is returned by invoking the function reference  the return statement in factory     ref  angular service vs angular factory  Second    Keep in mind all providers in AngularJS  value  constant  services  factories  are singletons    Third    Using one or the other  service or factory  is about code style  But  the common way in AngularJS is to use factory    Why        Because  The factory method is the most common way of getting objects into AngularJS dependency injection system  It is very flexible and can contain sophisticated creation logic  Since factories are regular functions  we can also take advantage of a new lexical scope to simulate  private  variables  This is very useful as we can hide implementation details of a given service       ref  http   www amazon com Mastering-Web-Application-Development-AngularJS dp 1782161821      Usage  Service   Could be useful for sharing utility functions that are useful to invoke by simply appending    to the injected function reference  Could also be run with injectedArg call this  or similar   Factory   Could be useful for returning a    class    function that can then be new ed to create instances   So  use a factory when you have complex logic in your service and you don t want expose this complexity    In other cases if you want to return an instance of a service just use service    But you ll see with time that you ll use factory in 80  of cases I think   For more details  http   blog manishchhabra com 2013 09 angularjs-service-vs-factory-with-example      UPDATE    Excellent post here    http   iffycan blogspot com ar 2013 05 angular-service-or-factory html      If you want your function to be called like a normal function  use   factory  If you want your function to be instantiated with the new   operator  use service  If you don t know the difference  use factory       UPDATE    AngularJS team does his work and give an explanation   http   docs angularjs org guide providers  And from this page         Factory and Service are the most commonly used recipes  The only difference between them is that Service recipe works better for objects of custom type  while Factory can produce JavaScript primitives and functions

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The concept for all these providers is much simpler than it initially appears  If you dissect a provider you and pull out the different parts it becomes very clear   To put it simply each one of these providers is a specialized version of the other  in this order  provider   factory   value   constant   service   So long the provider does what you can you can use the provider further down the chain which would result in writing less code  If it doesn t accomplish what you want you can go up the chain and you ll just have to write more code   This image illustrates what I mean  in this image you will see the code for a provider  with the portions highlighted showing you which portions of the provider could be used to create a factory  value  etc instead     source  simplygoodcode com     For more details and examples from the blog post where I got the image from go to  http   www simplygoodcode com 2015 11 the-difference-between-service-provider-and-factory-in-angularjs

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Factory and Service are the most commonly used method  The only difference between them is that the Service method works better for objects that need inheritance hierarchy  while the Factory can produce JavaScript primitives and functions   The Provider function is the core method and all the other ones are just syntactic sugar on it  You need it only if you are building a reusable piece of code that needs global configuration   There are five methods to create services  Value  Factory  Service  Provider and Constant  You can learn more about this here angular service  this article explain all this methods with practical demo examples

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Both the factory and the service result in singleton objects which are  able to be configured by providers and injected into controllers and run blocks  From the point of view of the injectee  there is absolutely no difference whether the object came from a factory or a service   So  when to use a factory  and when to use a service  It boils down to your coding preference  and nothing else  If you like the modular JS pattern then go for the factory  If you like the constructor function   class   style then go for the service  Note that both styles support private members   The advantage of the service might be that it s more intuitive from  the OOP point of view  create a  class   and  in conjunction with a provider  reuse the same code across modules  and vary the behavior of the instantiated objects simply by supplying different parameters to the constructor in a config block

User · Answer

There is nothing a Factory cannot do or does better in comparison with a Service  And vice verse  Factory just seems to be more popular  The reason for that is its convenience in handling private public members  Service would be more clumsy in this regard  When coding a Service you tend to make your object members public via    this    keyword and may suddenly find out that those public members are not visible to private methods  ie inner functions     var Service   function         public   this age   13       private   function getAge         return this age    private does not see public         console log  age      getAge          var s   new Service      prints  age  undefined    Angular uses the    new    keyword to create a service for you  so the instance Angular passes to the controller will have the same drawback  Of course you may overcome the problem by using this that   var Service   function       var that   this       public   this age   13       private   function getAge         return that age          console log  age      getAge          var s   new Service      prints  age  13      But with a large Service constant this that-ing would make the code poorly readable  Moreover  the Service prototypes will not see private members     only public will be available to them   var Service   function       var name    George        Service prototype getName   function       return this name    will not see a private member      var s   new Service    console log  name      s getName      prints  name  undefined    Summing it up  using Factory is more convenient  As Factory does not have these drawbacks  I would recommend using it by default

[angularjs] AngularJS : When to use service instead of factory

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