C#•3mo ago

fastest way to check if list doesn't contain null ?

I have a list of reference type (for example, list of string) as constructor parameter. Now i require that all of the list element must not be null. Everytime the object instance is created, the constructor will loop through the list to verify that none of the element is null. However, this have performance impact to immutable class where any modification require creating new instance of the class (because immutable class can't be modified). Is there faster way to check that list element cannot be null?

15 Replies

Keswiik•3mo ago

why not create a private internal constructor that bypasses this validation? You already know that any existing instances of your immutable class have passed said validation.

PotassiumOP•3mo ago

Hmm right, maybe i can add a second public constructor with additional parameter to older instance so that if user doesn't modify the list, it will get the list from the older instance instead and avoid the check. Is this a good design ?

Keswiik•3mo ago

i honestly have no idea what you mean by "second public constructor with additional parameter to older instance" how do users modify your immutable class?

PotassiumOP•3mo ago

I mean,it is immutable, the only way to modify immutable class is to create new instance of it

Keswiik•3mo ago

I am assuming you have an Add Remove etc methods that internally create a new instance of your immutable and return it

PotassiumOP•3mo ago

Yes

Keswiik•3mo ago

then there is no reason to expose the new constructor to consumers i would personally do something like

PotassiumOP•3mo ago

but my class have many field, it would require adding Add/Edit/Remove method for every single field wont it ? I want user to create new instance by themselves to modify the field

Keswiik•3mo ago

public class IdkWhatYourCollectionIs<T> {
    public IdkWhatYourCollectionIs(IEnumerable<T> source) : this(source, true) {}

    private IdkWhatYourCollectionIs(IEnumerable<T> source, bool validate) {
      // logic here
    }

    public IdkWhatYourCollectionIs<T> Add(T item) {
      // validate not null
      // copy internal collection
      // add item to new collection
      return new IdkWhatYourCollectionIs<T>(newCollection, false);
    }
}

public class IdkWhatYourCollectionIs<T> {
    public IdkWhatYourCollectionIs(IEnumerable<T> source) : this(source, true) {}

    private IdkWhatYourCollectionIs(IEnumerable<T> source, bool validate) {
      // logic here
    }

    public IdkWhatYourCollectionIs<T> Add(T item) {
      // validate not null
      // copy internal collection
      // add item to new collection
      return new IdkWhatYourCollectionIs<T>(newCollection, false);
    }
}

^ this is the approach I would take if you require the consumer to make all changes then you have no way of guaranteeing the data is safe / good without doing your own validation on every modification then you'll need to run validation since the user could have included null values ¯\_(ツ)_/¯

PotassiumOP•3mo ago

Hmm right Man this made me wish c# doesnt allow null by default Anyway txn

Keswiik•3mo ago

wdym null by default?

PotassiumOP•3mo ago

Reference type

Keswiik•3mo ago

reference types being nullable is pretty normal, it would be weird if c# didn't allow it by default considering you do need to make modifications to this class, is there any reason why you're making it an immutable?

PotassiumOP•3mo ago

Easiest way to make it thread safe. Maybe i should rethink it

Keswiik•3mo ago

well, what type of async / multithreaded access is this going to deal with?

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fastest way to check if list doesn't contain null ?