Feature #4862
closed
Added by postmodern (Hal Brodigan) about 13 years ago.
Updated over 12 years ago.
Description
Occasionally, it is necessary to convert a Struct to a Hash (especially when generating JSON from an Array of Structs). A Struct#to_hash method would be very useful in this situation.
class Struct
#
# Returns the Hash representation of the members and values within the struct.
#
def to_hash
new_hash = {}
each_pair do |member,value|
new_hash[member] = value
end
new_hash
end
end
def to_hash() Hash[members.zip(values)] end
A Struct doesn't respond to hardly any Hash methods in general. So #to_h
seems more appropriate.
Then again maybe I'm wrong b/c I was just surprised by the fact that a Struct doesn't have (or at least act like it has) instance_variables.
Struct.new(:a).new(1).instance_variables #=> []
Thomas Sawyer wrote:
Then again maybe I'm wrong b/c I was just surprised by the fact that a Struct doesn't have (or at least act like it has) instance_variables.
Struct.new(:a).new(1).instance_variables #=> []
Yeah, it is implemented with an array stored in the RStruct struct in MRI.
A Struct#to_hash method would be very useful in this situation.
I agree.
#to_hash is the right method name because there is no #to_h (but indeed it is somewhat inconsistent with #to_i, #to_int, ...)
Despite it's implementation, I thought Struct was intended to provide a convenient way to make quick classes. Which is why I assume it would have instance variables. I can understand though that it would be implemented in another fashion for speed. But I would still think the public interface to appear as if it were a typical sort of class.
Given it's current interface it hardly resembles a Hash at all. I think #each at least should act the same as a Hash if #to_hash would be added to it, but instead it acts like an Array:
s = Struct.new(:a, :b).new(1,2)
=> #
s.map{ |a| a }
=> [1, 2]
"because there is no #to_h (but indeed it is somewhat inconsistent with #to_i, #to_int, ...)"
Not just "somewhat". So I ignore all that heehawing and define #to_h wherever it makes sense when I need it. Why #to_h should be carved out as some odd exception seems to me just a lot of needless fuss over... what?
Struct does use instance variables, you just can't see them from ruby because they don't start with @
- Status changed from Open to Assigned
- Assignee set to matz (Yukihiro Matsumoto)
- Status changed from Assigned to Rejected
#to_hash protocol expects the object to be hash-compatible. Struct is not the case.
Matz.
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