[question] Is there a way to create a private instance variable?

[andyfleming]

I'm aware of instance and class variables, but is there a way to create a private instance variable?

class Person
  def initialize()
    @example_one = "instance variable"
    @@example_two = "static/class variable"
    # No way to create a private instance variable
  end
end

[RX14]

Instance variables are always private. The only way to "expose" an instance variable is through getters/setters, either manually created or using the getter, setter or property macros.

[andyfleming]

I see that now. Sorry about that.

For anyone else that comes across this, here's the snippet from the docs that shows creating a getter/setter for an instance variable.

class Person
  def initialize(name : String)
    @name = name
    @age = 0
  end

  def name
    @name
  end

  def age
    @age
  end
end

From https://crystal-lang.org/docs/syntax_and_semantics/new,_initialize_and_allocate.html

[mgarciaisaia]

Don't get confused - that code defines getters, but there are no setters there.

A setter looks like this:

def instvar=(value)
  @instvar = value
end

But the best way to deal with this is using the macros for defining getters, setters or accesors (both getter AND setter).

[andyfleming]

Thanks! Someone else explained the concepts a bit more clearly for me.

I opened an issue to improve the documentation here: crystal-lang/crystal-book#62