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C#•2y ago

❔ How does one hold a value in a private field in a controller?

So basically controller gets created for every request right? Problem is i have this field:

private Lesson _CurrentUserLesson

private Lesson _CurrentUserLesson

And i set it once the user creates a new lesson. However if you call another endpoint that uses that variable it becomes null, static wont do either as i read. So how do you approach this?

58 Replies

SUPER MEGA T REX•2y ago

Web servers are generally stateless You'd normally pass a lessonId or such parameter with subsequent requests And then load the lesson to do whatever it is you need to do with it

antimatter8189OP•2y ago

yeah but wont i have to make a DB call each time?

SUPER MEGA T REX•2y ago

Yeah (unless you cache it)

antimatter8189OP•2y ago

I see

SUPER MEGA T REX•2y ago

That's completely normal, though

antimatter8189OP•2y ago

So basically only services and managers go into the Di and into the service?

SUPER MEGA T REX•2y ago

You've lost me there I'm afraid

antimatter8189OP•2y ago

and a few consts well

    private readonly IGuidGenerator _guiGenerator;

    //Services And Managers - Utilizing Dependency Injection.
    private readonly AnswerComparisonManager _answerComparisonManager;
    private readonly AzureBlobStorageManager _azureBlobStorageManager;
    private readonly GoogleApiManager _googleApiManager;
    private readonly ILessonRepository _lessonRepository;
    private readonly OpenAiExtraction _openAiExtraction;

    //Private Members
    private Lesson _currentLesson;
    private LessonPhase _currentPhase;
    private LessonState _lessonState;
    private MySupportedLanguageCodes _dstLanguageCode;
    private MySupportedLanguageCodes _srcLanguageCode;
    private readonly BotSpeakSentences _botSpeakSentences = new();
    private List<Lesson> _userLessons;

    private const int _tryAgainAnswerAttemptsThreshold = 2;
    private const int _maxNumberOfAnswerAttempts = 5;
    private const int _numberOfPhasesUsedForExplaining = 5;
    private const int _maxNumberOfExplanationRequestsPerPhase = 3;

    private readonly IGuidGenerator _guiGenerator;

    //Services And Managers - Utilizing Dependency Injection.
    private readonly AnswerComparisonManager _answerComparisonManager;
    private readonly AzureBlobStorageManager _azureBlobStorageManager;
    private readonly GoogleApiManager _googleApiManager;
    private readonly ILessonRepository _lessonRepository;
    private readonly OpenAiExtraction _openAiExtraction;

    //Private Members
    private Lesson _currentLesson;
    private LessonPhase _currentPhase;
    private LessonState _lessonState;
    private MySupportedLanguageCodes _dstLanguageCode;
    private MySupportedLanguageCodes _srcLanguageCode;
    private readonly BotSpeakSentences _botSpeakSentences = new();
    private List<Lesson> _userLessons;

    private const int _tryAgainAnswerAttemptsThreshold = 2;
    private const int _maxNumberOfAnswerAttempts = 5;
    private const int _numberOfPhasesUsedForExplaining = 5;
    private const int _maxNumberOfExplanationRequestsPerPhase = 3;

phaseshift•2y ago

consts? "in the DI" ?

antimatter8189OP•2y ago

this is what im talking about

SUPER MEGA T REX•2y ago

So you've got a controller with all of those fields?

antimatter8189OP•2y ago

Its a service

phaseshift•2y ago

thats way way way too much if thats a controller

antimatter8189OP•2y ago

nah thats the LEssonAppSErvice so basically all the private members gotta go?

SUPER MEGA T REX•2y ago

For the most part, yeah

antimatter8189OP•2y ago

since i cant actually save em between requests unless they static

phaseshift•2y ago

yes. and please dont put static data on a controller 😅

SUPER MEGA T REX•2y ago

At what kind of level are you expecting this 'service' to live? At the API level? At a lower domain level?

antimatter8189OP•2y ago

yeah its a work in progress unsure what you mean You mean the lifetime of the service? IDK? basically its an app like whatsapp but voice based so a user logs in and stats a lesson creates new ones on the fly etc

SUPER MEGA T REX•2y ago

So is this a "domain" service as in any interface to your domain (a web API, a GUI, etc) can interact with it? Or is this service specific to your API?

antimatter8189OP•2y ago

Its not a domain service no, and there is no real controller really

antimatter8189OP•2y ago

https://docs.abp.io/en/abp/latest/API/Auto-API-Controllers

API/Auto API Controllers | Documentation Center | ABP.IO

Once you create an application service, you generally want to create an API controller to expose this service as an HTTP (REST) API endpoint. A typical API controller does nothing but redirects method

antimatter8189OP•2y ago

😄 it exposes the service as a controller

SUPER MEGA T REX•2y ago

Weird as hell but ok 🙂 Remove everything that's a field that realistically depends on the request e.g. _currentLesson Depend on the classes required to implement whatever functionality it is And everything else should be a parameter coming from each request (However that's wired up using whatever ABP is) Whether as a parameter from the request itself or from a property of the session (e.g. user id)

antimatter8189OP•2y ago

Ok thats good because i do have acess to the currentUser class I was just tripping about all the DB calls and the cost associated with getting that big ass json each time because lesson is an aggregateroot it pulls all its realted data Phases answers questions etc

SUPER MEGA T REX•2y ago

The cost of a database call generally pales in comparison to the HTTP roundtrip for the request anyhow

antimatter8189OP•2y ago

How many years you work with .net?

SUPER MEGA T REX•2y ago

Err, 8?

antimatter8189OP•2y ago

oh thats nice

SUPER MEGA T REX•2y ago

It's not, it means I'm getting old 🙂

antimatter8189OP•2y ago

.net getting younger each year tho the amount of features 😄 another thing

SUPER MEGA T REX•2y ago

I'm waiting for proper ADTs to come across from F# to C# then I'll be happy.

antimatter8189OP•2y ago

If i create a singelton with DI then does it live basically from the moment i start the server?

phaseshift•2y ago

no

antimatter8189OP•2y ago

and is the same for all requests till server shuts down

phaseshift•2y ago

when its first resolved

SUPER MEGA T REX•2y ago

Depends on how you register it

antimatter8189OP•2y ago

        context.Services.AddSingleton<OpenAiManager>();

        context.Services.AddSingleton<OpenAiManager>();

SUPER MEGA T REX•2y ago

Then like phaseshift says, it's created the first time it's resolved And then yes, the same instance will always be returned when it's resolved

antimatter8189OP•2y ago

Gotcha will have to change that then, OpenAi hallucinations are real

SUPER MEGA T REX•2y ago

There's also an overload to register an instance If you really wanted to control the instantiation

antimatter8189OP•2y ago

with an interface you mean?

SUPER MEGA T REX•2y ago

var foo = new OpenAiManager();
services.AddSingleton(foo);

var foo = new OpenAiManager();
services.AddSingleton(foo);

antimatter8189OP•2y ago

oh yeah i dont need that lol abp got a preconfigure methode gets called first thing So it basically registers it as soon as the server starts

SUPER MEGA T REX•2y ago

Registers yes, instantiates when it is first resolved Generally you can treat the two as the same

antimatter8189OP•2y ago

Oh yeah youre correct

SUPER MEGA T REX•2y ago

But the actual OpenAiManager constructor won't be called until something asks the service collection for one

antimatter8189OP•2y ago

yup makes sense

SUPER MEGA T REX•2y ago

Sounds like you've got it nailed

antimatter8189OP•2y ago

So basically

    public async Task<BookCacheItem> GetAsync(Guid bookId)
        {
            return await _cache.GetOrAddAsync(
                bookId.ToString(), //Cache key
                async () => await GetBookFromDatabaseAsync(bookId),
                () => new DistributedCacheEntryOptions
                {
                    AbsoluteExpiration = DateTimeOffset.Now.AddHours(1)
                }
            );
        }

    public async Task<BookCacheItem> GetAsync(Guid bookId)
        {
            return await _cache.GetOrAddAsync(
                bookId.ToString(), //Cache key
                async () => await GetBookFromDatabaseAsync(bookId),
                () => new DistributedCacheEntryOptions
                {
                    AbsoluteExpiration = DateTimeOffset.Now.AddHours(1)
                }
            );
        }

For each and every method? you always cache as much as you can i guess What dont you cache lets put it this way And thx alot 😄

SUPER MEGA T REX•2y ago

Caching is an extremely nuanced topic What to cache, how long to cache it etc completely depends on the data You'd generally use a cache to implement the same interface as the thing that retrieves the data, though E.g. IGetBookFromDatabase would be the interface, GetBookFromSqlDatabase physically goes to the DB, CachedGetBookFromDatabase takes a cache and an IGetBookFromDatabase So the caching is transparent to the consumer The service doesn't care whether it comes from a cache or not, it just asks for a book

antimatter8189OP•2y ago

Yeah makes perfect sense thx again bud, have a great evening

SUPER MEGA T REX•2y ago

You too, GL with your code Also if your cache is string keyed, make sure you identify it properly e.g. you don't want to store things with just their ids in case you store book id 1234 and then accidentally retrieve that book when trying to get user id 1234 🙂

antimatter8189OP•2y ago

yeah im using Guids everywhere to prevent such things You pro in efcore i guess?

SUPER MEGA T REX•2y ago

I don't use EF at all I'm afraid

antimatter8189OP•2y ago

oh snap well a question for another time then thx alot 😄

SUPER MEGA T REX•2y ago

No worries

Accord•2y ago

Looks like nothing has happened here. I will mark this as stale and this post will be archived until there is new activity.

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