From: Robert Klemme <shortcutter@...>
Date: 2011-10-02T04:02:06+09:00
Subject: Re: access hashmap objects

On Sat, Oct 1, 2011 at 3:28 PM, Sam s. <samuel.stuetz@gmail.com> wrote:
> I got objects inside of a hashmap. And they are packed as the following
> code says and I want to unpack them again to change their manipulate the
> data and pack it again in the same way. Or directly change each datum if
> that works.
>
> mutation_map = key => {
>          column_family => hash.collect{|k,v|
> _standard_insert_mutation(column_family, k, v, timestamp,
> options[:ttl])}
>        }

That's not a Hash but rather a partial description of how a Hash is created.

> def _standard_insert_mutation(column_family, column_name, value,
> timestamp, ttl = nil)
>      CassandraThrift::Mutation.new(
>        :column_or_supercolumn =>
> CassandraThrift::ColumnOrSuperColumn.new(
>          :column => CassandraThrift::Column.new(
>            :name      =>
> column_name_class(column_family).new(column_name).to_s,
>            :value     => value,
>            :timestamp => timestamp,
>            :ttl       => ttl
>          )
>        )
> Code from the fauna project on github. A ruby cassandra client.
>
> now I think I understand what happens in this bit of code, but if I have
> this mutation_map later in code and want to manipulate specific parts of
> it how would I do that.
> Like encrypting the whole map. I would need access to each bit and
> change it

A fairly simply way to do it would be to serialize it via Marshal and
encrypt the resulting binary sting.

> getting to the column_family I write mutation_map[key][column_family]
> How do I go from there? I have an object now and this object should have
> accessor methodes.
>
> I know java not as much about ruby. How do I access that data. Should
> simple for any ruby veteran but in all the tutorials they stick to such
> simple stuff that you don't learn this kind of things.

I am not sure what you are really up to.  Accessing members of a Hash
is fairly straightforward - for reading and writing.  You can easily
extend that to nested Hashes

irb(main):003:0> h={:k => {:j => {}}}
=> {:k=>{:j=>{}}}
irb(main):004:0> h[:k][:j][:i] = 123
=> 123
irb(main):005:0> h
=> {:k=>{:j=>{:i=>123}}}

Kind regards

robert

-- 
remember.guy do |as, often| as.you_can - without end
http://blog.rubybestpractices.com/