Architecture: The data layer - MAD Skills

With this episode of MAD skills we are starting a series of videos dedicated to architecture. In this video you'll learn about the data layer and its two basic components: repositories and data sources. We'll also cover data immutability, error handling, threading, testing and more tricks and recommendations with Developer Relations Engineer Jose Alcérreca.
Architecture Guide → goo.gle/mad-architecture
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Product: Android - General

[@ibrahimdisouki7666]

Thanks for the great video! I hope you talking about error handling across all layers and which layer is responsible for what, with a simple example!

[@tadeuszkurpiel6137]

Great! It is a lot of informatin! I think I have to watch this video many times, and deep dive into the additional documentation to fully understand all the topics mentioned here...

[@ookie218]

Awesome video! Thanks for the detail!

[@donturner1928]

Where does the MonsterRepository live? In the data lair

[@javiercabral-qb3pr]

0:32

[@vivekgupta5749]

Eagerly waiting for next.

[@codewiththeitalians]

Love the style 😎

[@ssverma1916]

Keeping separate model for Remote and Local data sources is good for long term ... Like: RemoteArticle and LocalArticle ... and expose "Article" domain object only from Repositories

[@pererikbergman]

Yes, agreed. But it's usually called DataEntity since you read it from the data layer, network database etc. and it's mapped to a DomainEntity.

[@kaeya1964]

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[@kaeya1964]

@per-erikbergman2980 s ss .l oi7i cyst is assesses 44444444s44444444444ss5ssssssssssss44s4ss5sss sssasssssssss4 ssss4s4sss4s4s4ßasaaaasa the aahh and a aaaaaaaaaasaaaaaaaaaaasaaaaaaaasa in a warm heart Thumping loud and A guava juices of all of us re re a a samsara asaaaaaaassaassaassaasßI588asset for the a

[@muhammadammar1809]

Good demonstration.I am waiting for the next

[@GanjaBro99]

Very good info. I started my architecting journey with MVP architecture. It could be an overwhelming experience, but totally worth the hassle.

[@NickButcher]

Jose is the MVP

[@user-fv4tl6tv4o]

Боольшое спасибо автору,классное видео)

[@donturner1928]

Great start to your modelling career, Jose

[@pcprincipal345]

Lots of great faces lost and left to rot in the over-complicated world of software development. Hopefully this one makes it and actually get a life. Sitting in front of a computer screen all day is not a life. I hate this job.

[@katherinekuan]

Nice overview Jose!! This video is a great "repository" of information! 😜

[@olohialli9289]

pun intended i guess. Lmao

[@angelterrero2011]

@@olohialli9289 nnnn kkikvk yo nnh

[@angelterrero2011]

Bbb

[@omartamtom]

Question, At 4:20 we need a mapper class to convert types between the article model, Where should we do the mapping? Repository or inside the client?

[@eliaspujols5015]

🔥🥂 Mad Skills

[@anqingma7186]

I found a small inconsistency in the naming of the Repository. The naming convention in the documentation is `NewLocalDataSource`, but in the video it is named `LocalNewDataSource`, a correction is suggested. doc:

[@uzairaslam4658]

At 00:26 -> business logic lives inside data layer. Should not this be the responsibility of domain layer?

[@Teguder123]

4:52 which one is better, throwing an exception (and then the flow will stop) or convert the error to an instance of sealed class (whose subclasses are success and several predefined types of errors)?

[@rohanmanchanda5250]

Hello from August 8, 2022.

[@heshansandeepa9471]

again, very nice

[@rajeetgoyal6879]

Great 🔥👏

[@peterfischer2748]

Thanks for the great video Jose! I'm curious why did the Android team decide to have the data layer depend on the domain layer and not the other way around?

[@ikroopsinghkalsi3810]

Yes +1

[@MrKogarou]

Seems to me that the domain layer is essentially the refactor layer. You can extract reused code down from the UI layer and up from the data layer. So it has to be adjacent to both.

[@sbmusicworld100]

Great 👍

[@heshansandeepa9471]

Very nice

[@pererikbergman]

What is the motivation behind moving business logic down to the data layer?

[@ivansanchez4808]

Cool video

[@florageorge7257]

I love this app for is a life best activity

[@dmaendeleo]

Neat🤜

[@swiffty1]

At 4:20 if you don't need certain fields for the article for certain layers then it becomes difficult to name the refined model. How many types of Article models can we have?

[@JoseAlcerreca]

ArticlesDb, ArticlesUI...

[@maxwellmapako3820]

"This is out of the scope of this video" I see a joke that can be made here.. Kotlin coroutine scope 🤣

[@levinunezmarte6667]

How do you test a repository with two different data sources (LocalDataSource and RemoteDataSource)? Should I create one interface and make local and remote data source classes implement this interface? -I saw this approach in one of Google's app samples, but I don't like it because you are forcing each class to implement methods they don't need- Or should I create two separate interfaces, one for local data source and another one for remote data source and then make the repository depend on these two interfaces? I would prefer the second approach, but honestly writing tests for 3 separate classes (Repository class, LocalDataSource class and Remote Data Source class) might be a bit of a hassle.

[@techaido]

1:21 Repositories Repositories don't contain business logic, Thats your infrastructure layer, it's just persistence. YOUR BUSINESS LOGIC is in your DOMAIN.

[@tjdah10]

What does the data layer say when it's initialized? Data da daaaaaa!

[@musa4900]

Perfect Architecture, but still after I have built many projects I don't believe we should always create "Repository per one Resource" and "Data Source per one Resource and Source Type". Yes, as I said before it is perfect architecture, but I don't think this should be implemented for all projects, maybe only for large huge projects, right? I used to create many many classes and files to follow previous architecture rules, and each time I wanted to refactor my data layer because of changing for example specific API Layer Data Source (which may responsible for 30% of all used APIs), this will cause to change many classes and files including their definitions, and in my opinion this is too much to do, there is no point of doing this. In my point of view, we should separate Repositories and Data Sources only if we have "need" to do this otherwise even if that considered as good from an architecture point, but still it is not proper to be implemented until being really needed. Any thoughts?

[@josealcerreca4841]

We recommend you do this for every app, even small ones. It's not a lot of effort and it's going to make it more maintainable and testable. How many endpoints were you using in your app?

[@mondoshigua]

📱🇨🇴🙋🏻‍♂️👍🏼🤝🏼

[@lifein0178]

Is it good practice to update local database on separate thread with the data received from networkDataSource...? suspend fun fetchNews(): List { try { val news = remoteNewsDataSource.fecthNews() Thread { localNewsDataScource.updateNews(news) }.start() return news; } catch(ex: Exception) { } return localNewsDataSource.fetchNews() }