“静态类型”和“动态类型”有何不同？

Question

根据Nim手册，变量类型是“静态类型”，而在内存中变量指向的实际值是“动态类型”。

它们为什么可以是不同的类型呢？我以为将错误的类型分配给变量会导致错误。

- dgo.a

Answer 1

import typetraits

type
  Person = ref object of RootObj
    name*: string
    age: int

  Student = ref object of Person # a student is a person
    id: int

method sayHi(p: Person) {.base.} =
  echo "I'm a person"

method sayHi(s: Student) =
  echo "I'm a student"

var student = Student(name: "Peter", age: 30, id: 10)
var person: Person = student # valid assignment to base type
echo person.repr # contains id as well
echo name(person.type) # static type = Person
person.sayHi() # dynamic type = I'm a student

- def-