i'm writing class myhashset imitates set class. elements of set contained hash items reading {element => true}. here how defined:
class myhashset attr_accessor :store def initialize @store = {} end def insert(el) @store.merge!(el => true) end def include?(el) @store[el] end def delete(el) @store.select! {|key,value| key != el} end def to_a @store.keys end def self.union(set) result=myhashset.new result.store=(self.store).merge(set.store) result end end the last method union should such if type commands:
set1=myhashset.new set2=myhashset.new set1.insert("mark hamill") set1.insert("harrison ford") set1.insert("anthony daniels") set2.insert("ewan mcgregor") set2.insert("natalie portman") set2.insert("anthony daniels") and try compute
set3=set1.union(set2) i should set3 variable, instance of myhashset such store is:
{"mark hamill"=>true, "harrison ford"=>true, "anthony daniels"=>true, "ewan mcgregor"=>true, "natalie portman"=>true} however, if try run undefined method error message:
`<main>': undefined method `union' #<myhashset:0x00000000f4e3b8> (nomethoderror) i don't understand why ruby not pick method.
you must use instance method not class method. , can use self.class.new insted of myhashset.new
like this
class myhashset attr_accessor :store def initialize @store = {} end def insert(el) @store.merge!(el => true) end def include?(el) @store[el] end def delete(el) @store.select! {|key,value| key != el} end def to_a @store.keys end def union(set) result = self.class.new result.store = self.store.merge(set.store) result end end output
set1=myhashset.new # => #<myhashset:0x1efea79 @store={}> set2=myhashset.new # => #<myhashset:0x34c75a @store={}> set1.insert("mark hamill") # => {"mark hamill" => true} set1.insert("harrison ford") # => {"mark hamill" => true, "harrison ford" => true} set1.insert("anthony daniels") # => {"mark hamill" => true, "harrison ford" => true, "anthony daniels" => true} set2.insert("ewan mcgregor") # => {"ewan mcgregor" => true} set2.insert("natalie portman") #=> {"ewan mcgregor" => true, "natalie portman" => true} set2.insert("anthony daniels") # => {"ewan mcgregor" => true, "natalie portman" => true, "anthony daniels" => true} set3 = set1.union(set2) # => #<myhashset:0x1c7cbad @store={"mark hamill"=>true, "harrison ford"=>true, "anthony daniels"=>true, "ewan mcgregor"=>true, "natalie portman"=>true}> btw:
maybe can modify initialize method better usage this
def initialize(store = nil) @store = store || {} end after can call union easly
def union(set) self.class.new(self.store.merge(set.store)) end so final clas looks this
class myhashset attr_accessor :store def initialize(store = nil) @store = store || {} end def insert(el) @store.merge!(el => true) end def include?(el) @store[el] end def delete(el) @store.select! { |key, value| key != el } end def to_a @store.keys end def union(set) self.class.new(self.store.merge(set.store)) end end 