Fuzion • Idioms • Idiom # 73: Create a factory

Idiom # 73: Create a factory

Fuzion does not support reflection and it is not intended to ever support reflection. So there is no way to dynamically create an instance of a feature whose name is given as a string, but we can statically compare the string against the name of known heirs in the factory.

Code

parent_factory (str String) Parent =>
  if      str = "A"     then A
  else if str = "XYZ"   then XYZ
  else if str = "heir1" then heir1
  else if str = "heir2" then heir2
  else
    panic "heir '$str' not known by parent_factory"

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parent_factory (str String) Parent =>
  if      str = "A"     then A
  else if str = "XYZ"   then XYZ
  else if str = "heir1" then heir1
  else if str = "heir2" then heir2
  else
    panic "heir '$str' not known by parent_factory"
 
 
הההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההה
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What are effects?

Running Example

ex73 is

  parent_factory (str String) Parent =>
    if      str = "A"     then A
    else if str = "XYZ"   then XYZ
    else if str = "heir1" then heir1
    else if str = "heir2" then heir2
    else
      panic "heir '$str' not known by parent_factory"

  # define Parent
  Parent ref is

  # define heirs
  A     : Parent is
  XYZ   : Parent is
  heir1 : Parent is
  heir2 : Parent is


  for
    s in ["A", "XYZ", "heir1", "heir2", "error"]
    h := parent_factory s
  do
    say "created $s: $h"

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ex73 is
  parent_factory (str String) Parent =>
    if      str = "A"     then A
    else if str = "XYZ"   then XYZ
    else if str = "heir1" then heir1
    else if str = "heir2" then heir2
    else
      panic "heir '$str' not known by parent_factory"
  # define Parent
  Parent ref is
  # define heirs
  A     : Parent is
  XYZ   : Parent is
  heir1 : Parent is
  heir2 : Parent is
  for
    s in ["A", "XYZ", "heir1", "heir2", "error"]
    h := parent_factory s
  do
    say "created $s: $h"
 
 
הההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההה
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What are effects?

last changed: 2025-05-13

next: Idiom # 74: Compute GCD