Re:Seven years of Go
by Someone on Thursday November 10, 2016 @04:08PM
(#12924360)
Type information isn't reflection. In C++, given a pointer, you can only discover that it points to a Foo if you know that Foos exist.
If you don't, you'll never be able to find the name of the type, whether it has a member named "Bar", what the type of that member is, whether it can be set, whether Foo has a method named "Baz", what its argument types are, etc.
Even if you do know Foo is a type, the programmer has to do most of that stuff. For example, one cannot write a function that prints all fields of an object passed to it without specifying its concrete type. Add a field, and you have to adjust that function.
The only thing you can reliably do is determine whether Foo implements a given interface (= abstract base class) but again, that's only if you know that interface exists. You cannot determine the name of a superclass or the depth of an object's class hierarchy, for instance.
If you don't, you'll never be able to find the name of the type, whether it has a member named "Bar", what the type of that member is, whether it can be set, whether Foo has a method named "Baz", what its argument types are, etc.
Even if you do know Foo is a type, the programmer has to do most of that stuff. For example, one cannot write a function that prints all fields of an object passed to it without specifying its concrete type. Add a field, and you have to adjust that function.
The only thing you can reliably do is determine whether Foo implements a given interface (= abstract base class) but again, that's only if you know that interface exists. You cannot determine the name of a superclass or the depth of an object's class hierarchy, for instance.