Struct visible only within a class/ code file ruby-CodePudding

I want to use structs within my classes to save on memory, but I want my code to be easily used by others.
Say I want to use a new Struct, name it "KE". I want this Struct to be only visible from within a class I, that would be use it. I.e., if anyone who uses my code defines elsewhere class/struct "KE", it won't override my "KE", and mine won't override theirs. Having it in the same code text file is good too.

CodePudding user response：

You can put your code into a module which will act as a namespace, e.g.:

module Foo
  KE = Struct.new(:name)

  # remaining code
end

Within the Foo namespace you can refer to the struct just via KE, e.g.:

module Foo
  # ...

  def self.build_ke(name)
    KE.new(name)
  end
end

Foo.build_ke('abc')
#=> #<struct Foo::KE name="abc">

Outside of Foo however, you have to use the Foo:: prefix:

Foo::KE.new('def')
#=> #<struct Foo::KE name="def">

Other KE constants won't interfere with your KE:

KE = :top_level

module Bar
  KE = :nested_in_bar
end

KE      #=> :top_level
Bar::KE #=> :nested_in_bar
Foo::KE #=> Foo::KE          # <- your struct

To "hide" the struct, you could make the constant private via private_constant:

module Foo
  KE = Struct.new(:name)
  private_constant :KE

  def self.build_ke(name)
    KE.new(name)
  end
end

Foo.build_ke #=> #<struct Foo::KE name="abc">
Foo::KE      #=> NameError: private constant Foo::KE referenced

Or you could use an anonymous struct by not assigning it to a constant in the first place, e.g. via a private class method:

module Foo
  def self.ke_class
    @ke_class ||= Struct.new(:name)
  end
  private_class_method :ke_class

  def self.build_ke(name)
    ke_class.new(name)
  end
end

Foo.build_ke('abc') #=> #<struct name="abc">
Foo.ke_class        #=> NoMethodError: private method `ke_class' called for Foo:Module