Nim by Example: Objects

Objects in Nim are a bit more rigid type than tuples.
We define a new object type by defining a new type. 
type Person = object
    name: string
    age: int
An object can be initialized by calling the object constructor. 
let alice = Person(name: "Alice", age: 25)
echo alice

echo alice.name, " is ", alice.age, " years old."
Uninitialized fields will be zero-valued. 
let bob = Person(name: "Bob")
echo bob.age, " == 0"
Order of parameters in constructor does not matter. 
let jane = Person(age: 28, name: "Jane")
echo jane
To create a custom constructor, define a proc returning an object instance. 
proc newPerson(name: string, age: int): Person =
    Person(name: name, age: age)

let joe = newPerson("Joe", 24)
echo joe
Reassigning an object will make a copy of it. 
var p1 = Person(name: "Bill")
var p2 = p1
p2.name = "Steve" # does not modify p1
echo p1, p2
In the references example, we will learn how to work with object references instead of object values. 
$ nim c -r objects.nim
(name: "Alice", age: 25)
Alice is 25 years old.
0 == 0
(name: "Jane", age: 28)
(name: "Joe", age: 24)
(name: "Bill", age: 0)(name: "Steve", age: 0)

Previously: Tuples
Next up: References

source | license