topic Re: Get instance method and design pattern in Application Development and Automation Discussions

Get instance method and design pattern

Former Member — Sun, 22 Mar 2009 21:26:33 GMT

Hi All,

1. I New to abap objects and i read the help and some stuff from the forum,

l like to now more about design pattern in abap objects,

2. I saw in some abap class the use of method of GET_INSTANCE i think it's from factory pattern , what is the pros. and cons to use this method ,when i should consider to use it ?

Thanks in Advance

Nina

Re: Get instance method and design pattern

Former Member — Mon, 23 Mar 2009 05:01:53 GMT

This message was moderated.

Re: Get instance method and design pattern

uwe_schieferstein — Mon, 23 Mar 2009 06:45:59 GMT

Hello Nina

A very good introduction into design patterns is the book "Head First: Design Patterns". Here you will find many good reasons why and when to use the factory pattern.

You should use the factory pattern when

- you want to prevent "direct" instantiation (i.e. using a public CONSTRUCTOR method) by the developer

- you want to hide the complexity of instantiation from the user of the class

- the instantiation creates an implementation of an interface and you want to keep control of which implementing class is returned

Regards

Uwe

Re: Get instance method and design pattern

seshatalpasai_madala — Mon, 23 Mar 2009 08:33:45 GMT

Hi,

For most of the classes where you find GET_INSTANCE method the classes instantiation would be marked as PRIVATE.

And the get_instance method would be public and static. This is to make sure that the instantiation of the class is done by the class itself in the get_instance mehod.

This is one way of getting the singleton pattern.

Regards,

Sesh

Re: Get instance method and design pattern

matt — Mon, 23 Mar 2009 08:55:25 GMT


> Hello Nina
> 
> A very good introduction into design patterns is the book "Head First: Design Patterns". Here you will find many good reasons why and when to use the factory pattern....

That's one of the essentials for me when I designing new applications. Very very useful!