Feature #11297: Allow private method of self to be called

• Status: Closed
• Assignee: -
• Target version: -

[soutaro (Soutaro Matsumoto)]

Ruby does not allow private method to be called if receiver is given. Calling private method with receiver is prohibited even if it is written as self, though the fact that the receiver is self is still clear.

This ticket is to propose to allow the private method to be called if its receiver is written as self.

The following Ruby program is to explain my idea.

class A
  private def f
  end
end

A.new.instance_eval do 
  f()              # Okay, without receiver
  self.f           # Currently NoMethodError, but should be okay in my opinion
  self.itself.f    # NoMethodError anyway; the receiver is not written as self
end

This change will allow to call private accessor method like self.title=.
It also will make refactoring to make a public method private easier. Currently, such kind of refactoring may require to rename duplicated local variables or add () to method calls.

[matz (Yukihiro Matsumoto)]

It changes the concept of private methods a little. It's OK to merge the patch if the document is updated at the same time..

Matz.

[nobu (Nobuyoshi Nakada)]

• Description updated (diff)

[jwmittag (Jörg W Mittag)]

Yukihiro Matsumoto wrote:

It changes the concept of private methods a little. It's OK to merge the patch if the document is updated at the same time..

It does change it, but it makes it much simpler in my opinion. It is basically "the receiver is statically the explicit literal special variable self or implicit." This gets rid of the current exception for private writer methods (self.foo = bar).

It also resolves the problems with private operator methods (self + bar) and compound assignments with private writers and/or private operators (self += bar, self.foo += bar, where either + or foo= or both are private). It removes pretty much all edge cases in one blow.

See also #9907 which would be simplified by this proposal. In particular, implementing the simple rule would make Charles Oliver Nutter's confusion go away (#9907-6, #9907-8), be consistent with Nobuyoshi Nakada's expectations (#9907-7) and alleviate Benoit Daloze's concerns about being decidable statically at parse time (#9907-9).

In fact, I believe that with this feature all of these should work:

#!/usr/bin/env ruby

class Private
  def doit
    self.foo = self
    self.foo **= self
    self.foo *= self
    self.foo /= self
    self.foo %= self
    self.foo += self
    self.foo -= self
    self.foo <<= self
    self.foo >>= self
    self.foo &= self
    self.foo |= self
    self.foo ^= self
    self.foo &&= self
    self.foo ||= self

    !self
    ~self
    +self
    self ** self
    -self
    self * self
    self / self
    self % self
    self + self
    self - self
    self << self
    self >> self
    self & self
    self | self
    self ^ self
    self < self
    self <= self
    self >= self
    self > self
    self == self
    self === self
    self != self
    self =~ self
    self !~ self
    self <=> self
    self[self, self]
    self[self, self] = self, self
    self.(self, self)
  end

  private

  attr_accessor :foo

  def !(*args)    p __method__, *args end
  def ~(*args)    p __method__, *args end
  def +@(*args)   p __method__, *args end
  def **(*args)   p __method__, *args end
  def -@(*args)   p __method__, *args end
  def *(*args)    p __method__, *args end
  def /(*args)    p __method__, *args end
  def %(*args)    p __method__, *args end
  def +(*args)    p __method__, *args end
  def -(*args)    p __method__, *args end
  def <<(*args)   p __method__, *args end
  def >>(*args)   p __method__, *args end
  def &(*args)    p __method__, *args end
  def |(*args)    p __method__, *args end
  def ^(*args)    p __method__, *args end
  def <(*args)    p __method__, *args end
  def <=(*args)   p __method__, *args end
  def >=(*args)   p __method__, *args end
  def >(*args)    p __method__, *args end
  def ==(*args)   p __method__, *args end
  def ===(*args)  p __method__, *args end
  def !=(*args)   p __method__, *args end
  def =~(*args)   p __method__, *args end
  def !~(*args)   p __method__, *args end
  def <=>(*args)  p __method__, *args end
  def [](*args)   p __method__, *args end
  def []=(*args)  p __method__, *args end
  def call(*args) p __method__, *args end
end

Private.new.doit

[matz (Yukihiro Matsumoto)]

• Related to Feature #16123: Allow calling a private method with `self.` added

[nobu (Nobuyoshi Nakada)]

• Related to deleted (Feature #16123: Allow calling a private method with `self.`)

[nobu (Nobuyoshi Nakada)]

• Has duplicate Feature #16123: Allow calling a private method with `self.` added

[dylants (Dylan Thacker-Smith)]

• Status changed from Open to Closed

Applied in changeset git|7fbd2f7cc247ee66e877ab3c88f0274834c6b6c7.

---

Allow calling a private method with self.

This makes it consistent with calling private attribute assignment
methods, which currently is allowed (e.g. self.value =).

Calling a private method in this way can be useful when trying to
assign the return value to a local variable with the same name.

[Feature #11297] [Feature #16123]

[nobu (Nobuyoshi Nakada)]

• Related to Bug #16947: private method unexpected behavior added