Feature #18736: self-p for method chain

• Status: Open
• Assignee: -
• Target version: -

[aDAVISk (Akito D. Kawamura)]

You may want to check object with p method at the middle of a method chain.
Here is my recomendation.

class Object
  def sp(method=nil, *args, &block)
    if method
        Kernel.p self.public_send(method, *args, &block)
    elsif block_given?
        Kernel.p block.call(self)
    else
      Kernel.p self
    end
    return self
  end
end

Example of usage:

1. check itself in the middle of a method-call

p [1,2,3].map{|x| x**2}.sp.map{|x| x**2}

• output

[1,4,9]
[1,16,81]

2. check its value in some string format

[1,2,3].sp{|x| "my List = #{x}"}

• output

"my List = [1,2,3]"

3. check its sum with an initial value

[1,2,3].sp(:sum,-10)

• output

-4

4. check its value with a map operation

[1,2,3].sp(:map){|x| x**2}

• output

[1,4,9]

5. check its value connected in string

[1,2,3].sp(:sum,""){|x| x.to_s}

• output

"123"

---

Your brush-up comments are welcomed. thx.

[sawa (Tsuyoshi Sawada)]

It just looks too ugly to me. What do you gain from passing the block to sp instead of the method that is originally supposed to handle it? The following conventional way is much more straightforward. (In addition, in your first example, why are you using p ... in one place instead of sp? It is inconsistent.)

[1, 4, 9].tap{|x| p x}.map{|x| x**2}.tap{|x| p x}
#>> [1, 4, 9]
#>> [1, 16, 81]
[1,2,3].tap{|x| p "my List = #{x}"}
#>>"my List = [1, 2, 3]"
[1,2,3].sum(-10).tap{|x| p x}
#>> -4
[1,2,3].map{|x| x**2}.tap{|x| p x}
#>>[1, 4, 9]
[1,2,3].sum("", &:to_s).tap{|x| p x}
#>>"123"

You may come to think that you rather want a method that would do tap{|x| p x}, but I think that was already proposed various times, and proposing that here would be a duplicate.

[mame (Yusuke Endoh)]

• Related to Feature #14609: Let `Kernel#p` without an argument print the receiver added

[aDAVISk (Akito D. Kawamura)]

That's exactly I meant. Thanks a lot, I call this topic closed. Sorry for the bad traffic.