What I want to do is have 2 nested hashes, the outer hash returning a new hash on an unknown key and the inner hash returning a space on an unknown key.
For example:
values = Hash.new # as described above
values[4][4] = "H" # The 4 is an unknown key, so a new Hash is formed # and the value of that inner hash's 4 key is "H"
values[5][6] # => " "
I got this to work correctly with the following (only ints are keys):
@value = []
0.upto(300) do |x|
@value[x] = Hash.new(" ")
end
But that is horrible.
So I've tried this:
value = Hash.new(Hash.new(" "))
But if you pass an object as the default value for a hash, it is not cloned for each unknown key.
So then this:
value = Hash.new { Hash.new(" ") }
But that has some problems as well:
irb(main):013:0> value = Hash.new {Hash.new(" ") }
=> {}
irb(main):014:0> value[5][6] = "H"
=> "H"
irb(main):015:0> value[5][6]
=> " "
irb(main):016:0> value[5][7] = "I"
=> "I"
irb(main):017:0> value[5][6]
=> " " # It just changed from what I set it to above.
Is there anyway to get this to work?
Daniel Finnie wrote:
What I want to do is have 2 nested hashes, the outer hash returning a new hash on an unknown key and the inner hash returning a space on an unknown key.
value = Hash.new {|h,k| h[k] = Hash.new {|h1,k1| h1[k1] = " "}}
p value[5][6] # ==> " "
value[5][6] = "H"
p value # ==> {5=>{6=>"H"}}
···
--
vjoel : Joel VanderWerf : path berkeley edu : 510 665 3407
Daniel
I was beat to it, but since I spent ten minutes figuring it out, here is my solution anyway 
require 'rubygems'
require 'spec'
# a subclass, instead of a re-opened base class... how un-rubyish 
class SpaceHash < Hash
def (key)
value = super(key)
value = self[key] = Hash.new(" ") unless value
value
end
end
context "SpaceHash" do
setup do
@space_hash = SpaceHash.new
@space_hash[5][6] = "H"
end
specify "unassigned keys return a space" do
@space_hash[5][5].should == " "
end
specify "assigned keys should return their value" do
@space_hash[5][6].should == "H"
end
specify "assigned another key to the second layer should not reassign othe keys" do
@space_hash[5][7] = "I"
@space_hash[5][6].should == "H"
end
end
Ashley
···
On Dec 09, 2006, at 11:32 pm, Daniel Finnie wrote:
What I want to do is have 2 nested hashes, the outer hash returning a new hash on an unknown key and the inner hash returning a space on an unknown key.
Joel VanderWerf wrote:
Daniel Finnie wrote:
What I want to do is have 2 nested hashes, the outer hash returning a new hash on an unknown key and the inner hash returning a space on an unknown key.
value = Hash.new {|h,k| h[k] = Hash.new {|h1,k1| h1[k1] = " "}}
p value[5][6] # ==> " "
value[5][6] = "H"
p value # ==> {5=>{6=>"H"}}
Another option, in case you don't want all those empty strings cluttering up your hash:
value = Hash.new {|h,k| h[k] = Hash.new {" "}}
p value[5][6] # ==> " "
p value # ==> {5=>{}}
value[5][6] = "H"
p value # ==> {5=>{6=>"H"}}
# But, with this variation, beware:
value[5][7] << "add some characters after the space"
p value[5][7] # ==> " "
···
--
vjoel : Joel VanderWerf : path berkeley edu : 510 665 3407
Thanks, that works perfectly! (I'm only storing 1 char strings)
Joel VanderWerf wrote:
···
Joel VanderWerf wrote:
Daniel Finnie wrote:
What I want to do is have 2 nested hashes, the outer hash returning a new hash on an unknown key and the inner hash returning a space on an unknown key.
value = Hash.new {|h,k| h[k] = Hash.new {|h1,k1| h1[k1] = " "}}
p value[5][6] # ==> " "
value[5][6] = "H"
p value # ==> {5=>{6=>"H"}}
Another option, in case you don't want all those empty strings cluttering up your hash:
value = Hash.new {|h,k| h[k] = Hash.new {" "}}
p value[5][6] # ==> " "
p value # ==> {5=>{}}
value[5][6] = "H"
p value # ==> {5=>{6=>"H"}}
# But, with this variation, beware:
value[5][7] << "add some characters after the space"
p value[5][7] # ==> " "