Default values for object fields

Object fields are allowed to have a constant default value. The type of field can be omitted if a default value is given.

  1. type
  2.   Foo = object
  3.     a: int = 2
  4.     b: float = 3.14
  5.     c = "I can have a default value"
  7.   Bar = ref object
  8.     a: int = 2
  9.     b: float = 3.14
  10.     c = "I can have a default value"

The explicit initialization uses these defaults which includes an object created with an object construction expression or the procedure default; a ref object created with an object construction expression or the procedure new; an array or a tuple with a subtype which has a default created with the procedure default.

  1. type
  2.   Foo = object
  3.     a: int = 2
  4.     b = 3.0
  5.   Bar = ref object
  6.     a: int = 2
  7.     b = 3.0
  9. block: # created with an object construction expression
  10.   let x = Foo()
  11.   assert x.a == 2 and x.b == 3.0
  13.   let y = Bar()
  14.   assert y.a == 2 and y.b == 3.0
  16. block: # created with an object construction expression
  17.   let x = default(Foo)
  18.   assert x.a == 2 and x.b == 3.0
  20.   let y = default(array[1, Foo])
  21.   assert y[0].a == 2 and y[0].b == 3.0
  23.   let z = default(tuple[x: Foo])
  24.   assert z.x.a == 2 and z.x.b == 3.0
  26. block: # created with the procedure `new`
  27.   let y = new Bar
  28.   assert y.a == 2 and y.b == 3.0