From: Hal Fulton Date: 2004-11-18T08:56:16+09:00 Subject: [ANN] SuperStruct Hello all... In connection with things discussed here recently (re Struct and OpenStruct), I've just released SuperStruct ("into the wild," as Dan Berger would say). Basically it allows you to create a Struct that is more classlike and can be treated more like an Array and/or Hash, with a few limitations. It creates accessors for each key, has predictable instance var names, etc. Whether it's truly useful remains to be seen. As Dave pointed out, a class with a lot of accessors is not well encapsulated. You may think this is worse than a Struct, but I like it better. YMMV. See http://sstruct.rubyforge.org or the blurb below. Thanks, Hal Fulton ==================================================== SuperStruct Hal Fulton Version 1.0 License: The Ruby License 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 are not allowed (it does obj.to_str or obj.to_s) - strings 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 = SuperStruct.new(:alpha) x = myStruct.new x.alpha # nil # A value assigned at construction may be retrieved myStruct = SuperStruct.new(:alpha) x = myStruct.new(234) x.alpha # 234 # Unassigned fields are nil myStruct = SuperStruct.new(:alpha,:beta) x = myStruct.new(234) x.beta # nil # An open structure may not construct with nonexistent fields myStruct = SuperStruct.open x = myStruct.new(234) # error # An open structure may assign fields not previously existing myStruct = SuperStruct.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 = SuperStruct.open x = myStruct.new x.foo # nil # A field (in an open struct) that is unassigned will be nil myStruct = SuperStruct.open x = myStruct.new y = x.foobar # A struct created with new rather than open cannot reference nonexistent # fields myStruct = SuperStruct.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 = SuperStruct.new("alpha") # to_a will return an array of values myStruct = SuperStruct.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 = SuperStruct.new(:alpha,"beta") x = myStruct.new assert_equal(["alpha","beta"],x.members) # Class method 'members' will return a list of members (as strings) myStruct = SuperStruct.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 = SuperStruct.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 = SuperStruct.new("alpha","beta","gamma") x = myStruct.new(7,8,9) b = meth(*x) # to_hash will return a hash with fields as keys myStruct = SuperStruct.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 = SuperStruct.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 = SuperStruct.new("alpha","beta","gamma") x = myStruct.new(7,8,9) y = x[:beta] # [offset,length] may be used as for arrays myStruct = SuperStruct.new("alpha","beta","gamma") x = myStruct.new(7,8,9) y = x[0,2] # Ranges may be used as for arrays myStruct = SuperStruct.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 = SuperStruct.open(:alpha) x = myStruct.new x.beta = 5 # Adding a field to an open struct adds it to the class also myStruct = SuperStruct.open(:alpha) x = myStruct.new x.beta = 5 # An array passed to SuperStruct.new need not be starred myStruct = SuperStruct.new(%w[alpha beta gamma]) x = myStruct.new # A hash passed to #set will set multiple values at once myStruct = SuperStruct.new(%w[alpha beta gamma]) x = myStruct.new hash = {"alpha"=>234,"beta"=>345,"gamma"=>456} x.set(hash) # ||= works properly x = SuperStruct.open.new x.foo ||= 333 x.bar = x.bar || 444 # attr_tester will create a ?-method myStruct = SuperStruct.new(:alive) myStruct.attr_tester :alive x = myStruct.new(true) x.alive? # true