objectDef

Nim macro that create a object type definition from a constructor proc.

Examples

objectDef macro transform following code

import objectDef

proc Foo() {.objectDef(false).} =
  fieldDef:
    x = 1
    y = 2

to

type
  Foo = object
    x: int
    y: int

proc initFoo(): Foo =
  result = Foo(x: 1, y: 2)

Transform follwoing code

proc Bar(x, y: int) {.objectDef(true).} =
  let t = getTime()
  fieldDef:
    a = {1: "one", 2: "two"}.toTable
    var
      b, c = x * y
      d, e = [x, y - x]
      f, g, h: string
    local = t.local
    t2 = t - initDuration(seconds = x)

  echo result.b
  echo result.t2

to

type
  Bar = ref object
    a: Table[int, string]
    b: int
    c: int
    d: array[0 .. 1, int]
    e: array[0 .. 1, int]
    f: string
    g: string
    h: string
    local: DateTime
    t2: Time

proc newBar(x, y: int): Bar =
  let t = getTime()
  result = Bar(a: toTable([(1, "one"), (2, "two")]), b: x * y, c: x * y, d: [x, y - x],
             e: [x, y - x], f: default(string), g: default(string), h: default(string),
             local: local(t), t2: t - initDuration(0, 0, 0, x, 0, 0, 0, 0))
  echo [result.b]
  echo [result.t2]

How to use

This macro works by adding objectDef pragma to your constructor proc. It read assignments and var statements under fieldDef and create an object type that has corresponding fields. New object type have same name to the input proc.

When isRef == false, object type is defined and init prefix is added to the input proc name. When isRef == true, ref object type is defined and new prefix is added to the input proc name. When the input proc is exported, new object type is also exported.

Limitations:

• Only assignments, var statements and comments are allowed under fieldDef.
• Generic proc is not supported.
• You can use fieldDef only once in a input proc.
• fieldDef must be placed under input proc and cannot be placed under other statments.