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by tekkk
1228 days ago
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Okay I guess I should provide more details. Constructor syntax fine? Jesus how come you can't use the constructor parameters as the default values but have to either resort to using `late` or that weird `: {}` after constructor like in C++, can't remember how it was. I just added `late` and thought whatever. Probably there are nuances I've missed but how come you had to reinvent that - thought it should be intuitive from the get-go. While stating itself to be statically typed you can also shoot yourself in the foot by simply using `as Type`, similar to TypeScript. Because that just assigns it to a type and doesn't cast it like you do it in say Rust. The extreme use of classes with `abstract class` and whatnot feels kinda 90's to me, just a lot of abstractions and for what? Just feels unnecessarily complicated for something seemingly simple. Maybe it's just little too enterprisey for my taste. Maybe that's it. I'm glad they are taking steps to improve it, I think making it more functional would help it. Even just to distinguish it from the other OOP languages. And how come simple state management seemed so difficult as well? I tried using my tried and true MobX which is implemented for Dart as well but was disappointed in its complexity and the fact it requires you to run a code generator to wrap your classes with observables. What? Insane. |
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This is a really good question. The reason is that it ensures that you can never see a field before it's initialized. In Java, you might think that you'll never observe a final field before it's been initialized but not so! In the constructor, you can call a method on `this` even before all fields have been definitely initialized. Inside that method (which might be overridden!), you can then read the field. It will be default initialized.
This means every time you create an object in Java, some extra code is running to default initialize all the fields just in case they get read before they're actually initialized. (I assume in some cases the compiler can prove it's not needed and eliminate it, but not in the general case).
It also means that the type system can't rely on fields being initialized for static safety. That in turn means that the compiler can't optimize based on that fact.
In Dart with the constructor initialization syntax, it's not syntactically possible to access any state on a new instance until after every single one of its initializers has run. That means that, in concert with null safety, if you have a non-nullable field, the compiler knows it will never ever be null and then can generate smaller, faster code based on that guarantee.
I agree the constructor initializer syntax is annoying and I wish we had something better, but it's there for a reason. Also, in practice, you often use `this.` or `super.` on the constructor parameters and avoid the initializers entirely.
> While stating itself to be statically typed you can also shoot yourself in the foot by simply using `as Type`, similar to TypeScript. Because that just assigns it to a type and doesn't cast it like you do it in say Rust.
An "as" expression is fully sound and will throw a runtime exception if the value isn't a valid instance of the cast type.
> The extreme use of classes with `abstract class` and whatnot feels kinda 90's to me, just a lot of abstractions and for what?
You don't have to use classes if you don't want to. You can define functions and variables all at the top level and write in a completely procedural or functional style if that's your jam. Some of the Dart packages I maintain are mostly functions.
> I think making it more functional would help it.
We're getting there. It's always had anonymous functions, closures, and plenty of higher-order functions in the collection API. We're adding pattern mataching and exhaustiveness checking now which should let you program in an algebraic datatype style.