Call for comments - Structure

Greetings, fellow Rubyists...

I am revisiting a small project that has lain dormant for
some time...

http://github.com/Hal9000/Structure

As I make changes and improvements, I'd be interested in
hearing your comments.

You're welcome to critique the idea itself, the implementation,
missing features, the code, the style, or whatever.

I've pasted the README here for your convenience.

Thanks,
Hal Fulton

------------------------

Structure
Hal Fulton
Version 1.0.3
License: The Ruby License

This is a newer version of the older "SuperStruct" (sstruct) library.

This is an easy way to create Struct-like classes; it converts easily
between hashes and arrays, and it allows OpenStruct-like dynamic naming
of members.

Unlike Struct, it creates a "real" class, and it has real instance variables
with predictable names.

A basic limitation is that the hash keys must be legal method names (unless
used with send()).

Basically, ss["alpha"], ss[:alpha], and ss.alpha all mean the same.


NOTES:


It's like a Struct...
  - you can pass in a list of symbols for accessors
  - it will create a class for you
but...
  - you don't have to pass in the class name
  - it returns a "real" class
    . instance variables have the expected names
    . you can reopen and add methods
  - it doesn't go into the Struct:: namespace
  - it preserves the order of the fields
  - you can use Strings instead of Symbols for the names

It's like an Array...
 - you can access the items by [number] and [number]=
but...
 - you can also access the items by ["name"] and ["name"]=
 - you can access the items by accessors

It's like an OpenStruct...
 - (if you use .open instead of .new) you can add fields
   automatically with x.field or x.field=val
but...
 - you can initialize it like a Struct
 - it preserves the order of the fields

It's like a Hash...
 - data can be accessed by ["name"]
but...
 - order (of entry or creation) is preserved
 - arbitrary objects as keys are not allowed (it does obj.to_str or obj.to_s)
 - keys must be valid method names

It's like Ara Howard's Named Array...
 - we can access elements by ["name"] or ["name"]=
but...
 - you can access the items by accessors
 - strings must be valid method names

It's like Florian Gross's Keyed List...
 (to be done)
but...
 - it preserves the order of the fields


Some examples: (see test cases)
--------------

  # Need not assign to existing fields (default to nil)
  myStruct = Structure.new(:alpha)
  x = myStruct.new
  x.alpha  # nil

  # A value assigned at construction may be retrieved
  myStruct = Structure.new(:alpha)
  x = myStruct.new(234)
  x.alpha  # 234

  # Unassigned fields are nil
  myStruct = Structure.new(:alpha,:beta)
  x = myStruct.new(234)
  x.beta  # nil

  # An open structure may not construct with nonexistent fields
  myStruct = Structure.open
  x = myStruct.new(234)  # error

  # An open structure may assign fields not previously existing
  myStruct = Structure.open
  x = myStruct.new
  x.foo = 123
  x.bar = 456

  # The act of retrieving a nonexistent field from an open struct will
  # create that field
  myStruct = Structure.open
  x = myStruct.new
  x.foo   # nil

  # A field (in an open struct) that is unassigned will be nil
  myStruct = Structure.open
  x = myStruct.new
  y = x.foobar

  # A struct created with new rather than open cannot reference nonexistent
  # fields
  myStruct = Structure.new
  x = myStruct.new
  x.foo  # error

  # Adding a field to a struct will create a writer and reader for that field

  # An open struct will also create a writer and a reader together

  # A field has a real writer and reader corresponding to it

  # A string will work as well as a symbol
  myStruct = Structure.new("alpha")

  # to_a will return an array of values
  myStruct = Structure.new("alpha","beta","gamma")
  x = myStruct.new(7,8,9)
  assert(x.to_a == [7,8,9])

  # Instance method 'members' will return a list of members (as strings)
  myStruct = Structure.new(:alpha,"beta")
  x = myStruct.new
  assert_equal(["alpha","beta"],x.members)

  # Class method 'members' will return a list of members (as strings)
  myStruct = Structure.new(:alpha,"beta")
  assert_equal(["alpha","beta"],myStruct.members)

  # to_ary will allow a struct to be treated like an array in
  # multiple assignment
  myStruct = Structure.new("alpha","beta","gamma")
  x = myStruct.new(7,8,9)
  a,b,c = x
  assert(b == 8)

  # to_ary will allow a struct to be treated like an array in
  # passed parameters
  myStruct = Structure.new("alpha","beta","gamma")
  x = myStruct.new(7,8,9)
  b = meth(*x)

  # to_hash will return a hash with fields as keys
  myStruct = Structure.new("alpha","beta","gamma")
  x = myStruct.new(7,8,9)
  h = x.to_hash
  assert_equal({"alpha"=>7,"beta"=>8,"gamma"=>9},h)

  # A field name (String) may be used in a hash-like notation
  myStruct = Structure.new("alpha","beta","gamma")
  x = myStruct.new(7,8,9)
  y = x["beta"]

  # A field name (Symbol) may be used in a hash-like notation
  myStruct = Structure.new("alpha","beta","gamma")
  x = myStruct.new(7,8,9)
  y = x[:beta]

  # [offset,length] may be used as for arrays
  myStruct = Structure.new("alpha","beta","gamma")
  x = myStruct.new(7,8,9)
  y = x[0,2]

  # Ranges may be used as for arrays
  myStruct = Structure.new("alpha","beta","gamma")
  x = myStruct.new(7,8,9)
  y = x[1..2]

  # Adding a field to an open struct adds it to the instance
  myStruct = Structure.open(:alpha)
  x = myStruct.new
  x.beta = 5

  # Adding a field to an open struct adds it to the class also
  myStruct = Structure.open(:alpha)
  x = myStruct.new
  x.beta = 5

  # An array passed to Structure.new need not be starred
  myStruct = Structure.new(%w[alpha beta gamma])
  x = myStruct.new

  # A hash passed to #assign will set multiple values at once
  myStruct = Structure.new(%w[alpha beta gamma])
  x = myStruct.new
  hash = {"alpha"=>234,"beta"=>345,"gamma"=>456}
  x.assign(hash)

  # ||= works properly
  x = Structure.open.new
  x.foo ||= 333
  x.bar = x.bar || 444

  # attr_tester will create a ?-method
  myStruct = Structure.new(:alive)
  myStruct.attr_tester :alive
  x = myStruct.new(true)
  x.alive?  # true