3 ms·

> getting the return type of a method and getting the input parameter names (+ types) Type information literally doesn't exist at runtime, though. Isn't it kin

by pitaj 8y ago

> getting the return type of a method and getting the input parameter names (+ types) Type information literally doesn't exist at runtime, though. Isn't it kind of ridiculous to compare languages like that?

orf 8y ago
When you're comparing the relative power of reflection within the language, absolutely not.
- untog 8y ago
  But what would you use that information for, given that the language has no types? A JS function has no guarantees of what type a function returns anyway. It's like taking issue with the fact that a car doesn't come equipped with skis.
  - stickfigure 8y ago
    It's like taking issue with the fact that a car doesn't come equipped with skis. To draw out that analogy... we live in Greenland. Cars with skis are surprisingly useful.
lopatin 8y ago
> Type information literally doesn't exist at runtime, though. Correct if I'm wrong, not all types get erased in Java. Doesn't type erasure only happen for generics? Say I have a non generic, plain Java class and want to inspect one of it's method's return types at runtime to see if it returns class A or class B. I can do that, right?
- stickfigure 8y ago
  Yes, you are correct. There are also a number of circumstances in which you can get generic type info - it isn't erased, for example, if you create a concrete subclass of a generic type.
- pitaj 8y ago
  I was talking about JavaScript. In JavaScript there are no typed functions or arguments, so that information doesn't exist period.
  - lopatin 8y ago
    Right, so I guess I'm not understanding your point about why comparing two languages like this is ridiculous. Java has a full blown runtime reflection system (it's "types exist at runtime"). JS doesn't. So Java wins in the reflection category.
    - tracker1 8y ago
      But in JS, reflection is pretty much not needed... I don't need to use reflection to see if an object has a quack method, or that I call it with the right types... I just call instance.quack() ... It's up to you as the developer to keep your interfaces and composition in line. It's actually WAY easier than with C# or Java. Since the use-case of reflection itself is largely unnecessary.
      - lopatin 8y ago
        Calling a method and seeing what happens is not a substitute for reflection. You can do that in Java too btw.

by pitaj 8y ago

orf 8y ago

When you're comparing the relative power of reflection within the language, absolutely not.

untog 8y ago
But what would you use that information for, given that the language has no types? A JS function has no guarantees of what type a function returns anyway. It's like taking issue with the fact that a car doesn't come equipped with skis.
- stickfigure 8y ago
  It's like taking issue with the fact that a car doesn't come equipped with skis. To draw out that analogy... we live in Greenland. Cars with skis are surprisingly useful.

lopatin 8y ago

> Type information literally doesn't exist at runtime, though. Correct if I'm wrong, not all types get erased in Java. Doesn't type erasure only happen for generics? Say I have a non generic, plain Java class and want to inspect one of it's method's return types at runtime to see if it returns class A or class B. I can do that, right?

stickfigure 8y ago
Yes, you are correct. There are also a number of circumstances in which you can get generic type info - it isn't erased, for example, if you create a concrete subclass of a generic type.
pitaj 8y ago
I was talking about JavaScript. In JavaScript there are no typed functions or arguments, so that information doesn't exist period.
- lopatin 8y ago
  Right, so I guess I'm not understanding your point about why comparing two languages like this is ridiculous. Java has a full blown runtime reflection system (it's "types exist at runtime"). JS doesn't. So Java wins in the reflection category.
  - tracker1 8y ago
    But in JS, reflection is pretty much not needed... I don't need to use reflection to see if an object has a quack method, or that I call it with the right types... I just call instance.quack() ... It's up to you as the developer to keep your interfaces and composition in line. It's actually WAY easier than with C# or Java. Since the use-case of reflection itself is largely unnecessary.
    - lopatin 8y ago
      Calling a method and seeing what happens is not a substitute for reflection. You can do that in Java too btw.