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How do you guarantee that what is added to a list (for instance) is a Dog, and not a Cat? If you want strongly typed language support (and I do), then generics

How do you guarantee that what is added to a list (for instance) is a Dog, and not a Cat? If you want strongly typed language support (and I do), then generics make it vastly easier to write maintainable code. A generic doesn't mean "anything goes" - it means "You will definitely get the thing that you specified".

SideburnsOfDoom 14y ago
In Javascript or any other duck-typed language, you don't have that guarantee. You don't actually care that it's a Dog BTW, just that it has a method called Bark(), if that's what you call on it. You make sure that your code only puts dog-like objects into the list, either by writing tests or by reading the code and praying. But the system of putting objects into lists is really, really simple. I see the benefit of strong typing and I use it all the time. Generics are an epicycle that IMHO sits poorly with JavaScript.
- AndrewDucker 14y ago
  Exactly. This is _not_ Javascript. It's Typescript, which compiles into Javascript, but adds in guarantees that, for instance, what I'm getting _is_ a dog.
  - SideburnsOfDoom 14y ago
    Typescript is not JavaScript, but all JavaScript is TypeScript, including JavaScript that works as discussed above. It's just a bit funny that in Typescript are both a language that benefits from having generics and a language that doesn't need them.
- chanon 14y ago
  > You don't actually care that it's a Dog BTW, just that it has a method called Bark(), if that's what you call on it. This is exactly where TypeScript helps. With the way TypeScript interfaces work, you can define an interface interface Barker { Bark(); } And have an array of Barkers where each object's class doesn't have to explicitly say that it implements Barker. Ex. class Dog { Bark() {console.log('woof');} } class Cat { Meow() {console.log('meow');} } var barkers: Barker[]; // array of Barkers barkers.push(new Dog()); // compiles barkers.push(new Cat()); // won't compile Here Dog doesn't have to explicitly declare that it implements Barker. The TypeScript compiler automatically verifies that it does by the fact that it has a Bark() method. In TypeScript, Arrays already support this level of type checking. With generics, the static type checking will be able to cover a lot more code so that you don't have to depend on writing tests.
  - SideburnsOfDoom 14y ago
    I use interfaces all the time, and like generics, they are a way of getting around the limitations of a strict type system, at the cost of making the type system more complex. I may as well say "Interfaces are an epicycle that IMHO sits poorly with JavaScript." There are good things about strong typing, but it's astonishing how many language constructs can be thrown away if you don't have it.
    - AndrewDucker 14y ago
      Well, yes. You lose huge amounts if you don't have strong typing. After all, "naturally", nothing is strongly typed. Typing was added to languages so that you would have guarantees about what form your data would take.

SideburnsOfDoom 14y ago

In Javascript or any other duck-typed language, you don't have that guarantee. You don't actually care that it's a Dog BTW, just that it has a method called Bark(), if that's what you call on it. You make sure that your code only puts dog-like objects into the list, either by writing tests or by reading the code and praying. But the system of putting objects into lists is really, really simple. I see the benefit of strong typing and I use it all the time. Generics are an epicycle that IMHO sits poorly with JavaScript.

AndrewDucker 14y ago
Exactly. This is _not_ Javascript. It's Typescript, which compiles into Javascript, but adds in guarantees that, for instance, what I'm getting _is_ a dog.
- SideburnsOfDoom 14y ago
  Typescript is not JavaScript, but all JavaScript is TypeScript, including JavaScript that works as discussed above. It's just a bit funny that in Typescript are both a language that benefits from having generics and a language that doesn't need them.
chanon 14y ago
> You don't actually care that it's a Dog BTW, just that it has a method called Bark(), if that's what you call on it. This is exactly where TypeScript helps. With the way TypeScript interfaces work, you can define an interface interface Barker { Bark(); } And have an array of Barkers where each object's class doesn't have to explicitly say that it implements Barker. Ex. class Dog { Bark() {console.log('woof');} } class Cat { Meow() {console.log('meow');} } var barkers: Barker[]; // array of Barkers barkers.push(new Dog()); // compiles barkers.push(new Cat()); // won't compile Here Dog doesn't have to explicitly declare that it implements Barker. The TypeScript compiler automatically verifies that it does by the fact that it has a Bark() method. In TypeScript, Arrays already support this level of type checking. With generics, the static type checking will be able to cover a lot more code so that you don't have to depend on writing tests.
- SideburnsOfDoom 14y ago
  I use interfaces all the time, and like generics, they are a way of getting around the limitations of a strict type system, at the cost of making the type system more complex. I may as well say "Interfaces are an epicycle that IMHO sits poorly with JavaScript." There are good things about strong typing, but it's astonishing how many language constructs can be thrown away if you don't have it.
  - AndrewDucker 14y ago
    Well, yes. You lose huge amounts if you don't have strong typing. After all, "naturally", nothing is strongly typed. Typing was added to languages so that you would have guarantees about what form your data would take.