Feature #4621: NilClass#to_hash

• Status: Rejected
• Assignee: matz (Yukihiro Matsumoto)
• Target version: -

[sawa (Tsuyoshi Sawada)]

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Various methods defined on NilClass are handy to avoid Method undefined on NilClass errors. For example,

• to_a for multiple dimensioned array when there might not be some values for some indices:

    array[i].to_a[j].to_a[k]
  

• to_s for pattern match that might fail:

    string[regex].to_s*2
  

• to_i, to_f, to_c for index search that might fail, etc:

    array.index(element).to_i*3
  

But there is no NilClass#to_hash even though there is Hash#to_hash. If such method existed (equivalent to class NilClass; def to_hash; {} end end), then we would be able to do:

• to_hash for multiple embedded hash when there might not be some values for some keys:

    hash[:a].to_hash[:b].to_hash[:c]
  

Is there any reason why to_a, to_s, to_i, to_f, to_c are all defined on NilClass but not for to_hash? If there is not, I would like to request this feature.
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[naruse (Yui NARUSE)]

• Category set to core
• Status changed from Open to Assigned
• Assignee set to matz (Yukihiro Matsumoto)

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[matz (Yukihiro Matsumoto)]

• Status changed from Assigned to Rejected

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[matz (Yukihiro Matsumoto)]

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Hi,

In message "Re: [ruby-core:35924] [Ruby 1.9 - Feature #4621][Assigned] NilClass#to_hash"
on Wed, 27 Apr 2011 16:46:01 +0900, Yui NARUSE [e-mail] writes:

|Is there any reason why to_a, to_s, to_i, to_f, to_c are all defined on NilClass but not for to_hash? If there is not, I would like to request this feature.

to_a, etc. are explicit conversion methods, whereas to_int, to_hash,
etc. are implicit conversion methods. I don't see any good reason to
add implicit conversion methods to nil.

						matz.

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