I created a small “lab tool” that makes life easier for me. It’s
basically a Hash that you can’t put values into, the values can only
be obtained from a method that you define. I created it with the idea
that a calculation should only have to be done once. I paste the
README file below.
Please let me know what you think!
Best regards,
Fredrik J.
NAME
methodhash
SYNOPSIS
A Hash subclass for automatic storage of values obtained from a
method
defined by the user. Useful for lengthy calculations on large
datasets.
URI
INSTALL
gem install methodhash
DESCRIPTION
A Hash subclass that defines its values from a specified method.
Use it by creating a subclass of MethodHash, and define a method
with the name “mymethod” in it.
Like this (same code in samples/samples.rb):
1. Simple use
class AddOne < MethodHash
def mymethod(a)
sleep 3
a + 1
end
end
a = AddOne.new
a # {}
a[1] # 2
a[7] # 8
a # {1=>2, 7=>8}
puts a.dump # — !map:AddOne
# 1: 2
# 7: 8
2. With a file
b = AddOne.new ‘/tmp/one.yml’
b # {}
b[1] # 2
b.dump # ‘/tmp/one.yml’
c = AddOne.new ‘/tmp/one.yml’
puts c.inspect # {1=>2}
3. Some protection against data corruption.
class AddTwo < MethodHash
def mymethod(a)
a + 2
end
end
begin
d = AddTwo.new ‘/tmp/one.yml’ # ArgumentError: Path holds class
AddOne
rescue
puts $!
end
4. Saving exceptions arising from mymethod.
class AddOneFaulty < MethodHash
def mymethod(a)
rand(2)==0 ? raise(“Epic Fail!”) : a+1
end
end
e = AddOneFaulty.new
e[1] # RuntimeError: Epic Fail! # If something bad
happened
e # {1=>“ERROR: Epic Fail!”}
e.retry_errors # false
e[1] # RuntimeError: Epic Fail! # Still keeping
the error
e.retry_errors=true # true
e[1] # 2 # If better luck
this time
e # {1=>2}
5. A more complex setting
class AddThree < MethodHash
def initialize(path1=nil, path2=nil, mypath=nil)
@one = AddOne.new(path1)
@two = AddTwo.new(path2)
super(mypath)
end
def mymethod(a)
@one[a] + @two[a] - a
end
def dump
@one.dump
@two.dump
super
end
end
f = AddThree.new( ‘/tmp/one.yml’, ‘/tmp/two.yml’)
puts f[3]
f.dump
6. With two arguments
class Add < MethodHash
def mymethod(a,b)
a + b
end
end
HISTORY
0.5.0
Initial version
