James is right: the format of Marshal is not guaranteed to be portable across Ruby versions. Nevertheless some types do work.
Btw, Marshal's format is binary. Which means two things
1. you should open files in binary mode,
2. printing methods like #puts are not guaranteed to work.
If you observe these rules you can make it work with Time...
robert@fussel:~$ ruby1.8 -e 'File.open("x","wb"){|i|Marshal.dump(Time.now,i)}'
robert@fussel:~$ ls -l x
-rw-r--r-- 1 robert robert 18 2010-01-07 13:44 x
robert@fussel:~$ ruby19 -e 'p(File.open("x","rb"){|i|Marshal.load(i)})'
2010-01-07 13:44:40 +0100
robert@fussel:~$
... but apparently neither Date nor DateTime:
robert@fussel:~$ ruby1.8 -r date -e 'File.open("x","wb"){|i|Marshal.dump(Date.today,i)}'
robert@fussel:~$ ruby19 -r date -e 'p(File.open("x","rb"){|i|Marshal.load(i)})'
-e:1:in `load': class Date needs to have method `_load' (TypeError)
from -e:1:in `block in <main>'
from -e:1:in `open'
from -e:1:in `<main>'
robert@fussel:~$
robert@fussel:~$ ruby1.8 -r date -e 'File.open("x","wb"){|i|Marshal.dump(DateTime.now,i)}'
robert@fussel:~$ ruby19 -r date -e 'p(File.open("x","rb"){|i|Marshal.load(i)})'
-e:1:in `load': class DateTime needs to have method `_load' (TypeError)
from -e:1:in `block in <main>'
from -e:1:in `open'
from -e:1:in `<main>'
robert@fussel:~$
It does work for Date and DateTime when only using one version
robert@fussel:~$ ruby19 -r date -e 'File.open("x","wb"){|i|Marshal.dump(DateTime.now,i)}'
robert@fussel:~$ ruby19 -r date -e 'p(File.open("x","rb"){|i|Marshal.load(i)})'
#<DateTime: 2010-01-07T13:54:15+01:00 (2356995876177376393/960000000000,1/24,2299161)>
robert@fussel:~$ ruby19 -r date -e 'File.open("x","wb"){|i|Marshal.dump(Date.today,i)}'
robert@fussel:~$ ruby19 -r date -e 'p(File.open("x","rb"){|i|Marshal.load(i)})'
#<Date: 2010-01-07 (4910407/2,0,2299161)>
robert@fussel:~$
You have quite a few options:
1. use a type that works, e.g. String:
robert@fussel:~$ ruby1.8 -r date -e 'File.open("x","wb"){|i|Marshal.dump(Date.today.strftime,i)}'
robert@fussel:~$ ruby19 -r date -e 'p(Date.strptime(File.open("x","rb"){|i|Marshal.load(i)}))'
#<Date: 2010-01-07 (4910407/2,0,2299161)>
robert@fussel:~$
2. create custom Marshalling and demarshalling methods which use types that work.
3. create your custom date type which encapsulates a Date but uses customized Marshal serialization.
You can see an example for customized persistence in section "Custom Persistence" on http://blog.rubybestpractices.com/posts/rklemme/018-Complete_Class.html .
4. you use another serialization mechanism, like Yaml:
robert@fussel:~$ ruby1.8 -r date -r yaml -e 'File.open("x","wb"){|i|YAML.dump(Date.today,i)}'
robert@fussel:~$ ruby19 -r date -r yaml -e 'p(File.open("x","rb"){|i|YAML.load(i)})'
#<Date: 2010-01-07 (4910407/2,0,2299161)>
robert@fussel:~$
5. use yet another completely different format.
There are probably more options...
Kind regards
robert
···
On 01/07/2010 11:16 AM, Florian Odronitz wrote:
Hi,
I am trying to marshal objects with ruby 1.8 and read them with 1.9 but
I get an error on date objects:
ruby 1.8:
f=File.new('/tmp/date', 'w+'); f.puts Marshal.dump(Date.today); f.close
ruby 1.9:
m=File.read('/tmp/date'); Marshal.load(m)
gives me:
class Date needs to have method `_load' (TypeError)
The versions of Marshal are identical, but in 1.8, Date has a _dump and
_load method, in 1.9 it does not.
Am I missing something or is this a bug?
Any hints are appreciated.
--
remember.guy do |as, often| as.you_can - without end
http://blog.rubybestpractices.com/
