# State-0.4.2

**URL:** <https://www.ruby-forum.com/t/state-0-4-2/148243>\
**Category:** Ruby\
**Created:** [September 10, 2008, 9:32pm UTC](https://www.ruby-forum.com/t/state-0-4-2/148243 "2008-09-10T21:32:47Z")\
**Posts on this page:** 1\
**Page:** 1

<div class="post-metadata">

**Author:** ![ahoward](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/779978/32.png) [@ahoward](https://www.ruby-forum.com/u/ahoward)\
**Post date:** [September 10, 2008, 9:32pm UTC](https://www.ruby-forum.com/t/state-0-4-2/148243/1 "2008-09-10T21:32:47Z")

</div>

NAME  
state

SYNOPSIS  
platform agnostic persistent state for ruby processes based on sqlite

DESCRIPTION  
state provides an extremely simple to use state mechanism for ruby  
programs  
which require state between invocations. the storage is based on  
sqlite and  
is therefore platform agnostic. using state is no more difficult  
that using  
a hash - only that hash will persist between invocations your ruby  
program.  
see the samples and specs for details.

INSTALL  
gem install state

URIS  
[http://codeforpeople.com/lib/ruby/](http://codeforpeople.com/lib/ruby/)  
[http://rubyforge.org/projects/codeforpeople/](http://rubyforge.org/projects/codeforpeople/)

SAMPLES

\<========\< sample/a.rb \>========\>

~ \> cat sample/a.rb

```
 require 'state'

 # state provides persistent state for processes. usage requires

```

simply  
# accesses the state in a hash-like way.  
#

```
 # one process can create state
 #
   child do
     State.clear
     State['key'] = 'value'
   end

 # and later processes can have access to it
 #
   2.times do |i|
     child do
       value = State['key']
       puts "child[#{ i }] => #{ value.inspect }"
     end
   end

 BEGIN {
   # we use fork just for demonstation, but this works on windows

```

too 😉  
#  
def child &block  
Process.waitpid fork(&block)  
end  
}

~ \> ruby sample/a.rb

```
 child[0] => "value"
 child[1] => "value"

```

\<========\< sample/b.rb \>========\>

~ \> cat sample/b.rb

```
 require 'state'

 # state will store it's db in a subdirectory (.state) of your

```

home directory,  
# the default database is ~/.state/global, but you may specify a  
name to  
# create a new database  
#

```
   db = State.for 'foobar'

   db.clear

   puts db.path

   10.times{|i| db[i] = i}

   puts db.keys.inspect

```

~ \> ruby sample/b.rb

```
 /Users/ahoward/.state/foobar
 [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

```

\<========\< sample/c.rb \>========\>

~ \> cat sample/c.rb

```
 require 'state'

 # of course you can specify and absolute path
 #

   db = State.for :path => '/tmp/state'

   db.clear

   puts db.path

```

~ \> ruby sample/c.rb

```
 /tmp/state

```

\<========\< sample/d.rb \>========\>

~ \> cat sample/d.rb

```
 require 'state'

 # in general the interface for state is like that of a hash, see

```

the specs for  
# more details

```
   db = State.for 'foobar'

   db.clear

   10.times{|i| db[i] = i**2}
   5.times{|i| db.delete i}

   p db.keys
   p db.values

 # use the update method for atomic read-update of a key/val pair

   db['key'] = 42

   p :current => db['key']

   db.update 'key' do |old|
     p :old => old
     new = 42.0
   end

   p :update => db['key']

```

~ \> ruby sample/d.rb

```
 [5, 6, 7, 8, 9]
 [25, 36, 49, 64, 81]
 {:current=>42}
 {:old=>42}
 {:update=>42.0}

```

HISTORY  
0.4.2  
initial version

AUTHORS  
ara.t.howard

a @ [http://codeforpeople.com/](http://codeforpeople.com/)