Forum: Ruby writing on yaml file

Hi guys,

Is it possible for me to write on existing yaml file (i.e add contents
or change contents) using ruby prgramming? Is there any parser available
out there?

Nizam

On 01/25/2011 07:09 PM, Kamarulnizam Rahim wrote:
> Hi guys,
>
> Is it possible for me to write on existing yaml file (i.e add contents
> or change contents) using ruby prgramming? Is there any parser available
> out there?

The standard library defines the YAML class which can parse and emit
YAML documents.  There are quite a few examples out there.  I tried a
couple from here that seemed to work:

http://yaml4r.sourceforge.net/doc/page/examples.htm

Some code to get you started:

require 'yaml'
# Load the file.
yaml = YAML.load_stream(File.open('myfile.yaml'))
# Add a new key-value pair to the root of the first document.
yaml.documents[0]['new_key'] = 'new_value'
File.open('myfile.yaml', 'w') do |file|
  file.write(yaml.emit)
end

The above code assumes that you have a valid YAML file in myfile.yaml.
the first document in that file must have key-value pairs at the root.

-Jeremy

Am 26.01.2011 05:00, schrieb Jeremy Bopp:
>
>   file.write(yaml.emit)
> end
>
> The above code assumes that you have a valid YAML file in myfile.yaml.
> the first document in that file must have key-value pairs at the root.
>
> -Jeremy
>
>
You can use the YAML module more or less the same way as Marshal,
therefore the following is a bit easier I suppose. It parses the whole
YAML file and converts it into an appropriate data structure (most
likely a hash) with which you can work. Then call YAML.dump with the
modified object and the file where you want to save it in.

-------------------------------------------------
√ quintus@hades => ~
$ cat test.yml
---
a: 5
b: abcdef
√ quintus@hades => ~
$ irb
irb(main):001:0> require "yaml"
=> true
irb(main):002:0> hsh = YAML.load_file("test.yml")
=> {"a"=>5, "b"=>"abcdef"}
irb(main):003:0> hsh["c"] = 12345
=> 12345
irb(main):004:0> File.open("test.yml", "w"){|f| YAML.dump(hsh, f)}
=> #<File:test.yml (closed)>
irb(main):005:0> exit
√ quintus@hades => ~
$ cat test.yml
---
a: 5
b: abcdef
c: 12345
√ quintus@hades => ~
$

Thanks for the post!!

Nizam

When i load the following code:

convert_yaml = YAML::load_file('nizam.yaml')
    pp 
convert_yaml["System"]["Environmental"]["children"][2]["children"]
    nizam =
         [{"name"=>"nizam",
           "type"=>"Objective",
           "subtype"=>"None",
           "components"=>
            [{"type"=>"ContentBox",
              "title"=>"Audit",
              "args"=>{:content=>"None\n"}},
             {"type"=>"ChildListingComponent",
              "title"=>"Current Targets for the Audit Objective:"}]}]
    File.open("nizam.yaml", "w"){|f| YAML.dump(nizam, f)}

This error appears:

C:/Users/Hekmatyer/Documents/NetBeansProjects/Nizam_BARU/lib/Environmental.rb:167:in 
`[]': can't convert String into Integer (TypeError)

What seems to be the problem? Thanks

Nizam

I also alter some of the codes:

convert_yaml = YAML::load_file('nizam.yaml')
    pp 
convert_yaml["System"]["Environmental"]["children"][2]["children"]
    convert_yaml["System"]=
         [{"name"=>"nizam",
           "type"=>"Objective",
           "subtype"=>"None",
           "components"=>
            [{"type"=>"ContentBox",
              "title"=>"Audit",
              "args"=>{:content=>"None\n"}},
             {"type"=>"ChildListingComponent",
              "title"=>"Current Targets for the Audit Objective:"}]}]
    File.open("nizam.yaml", "w"){|f| YAML.dump(convert_yaml.to_yaml, f)}

But the same error appears.

Nizam

On 01/26/2011 08:03 PM, Kamarulnizam Rahim wrote:
>             [{"type"=>"ContentBox",
>               "title"=>"Audit",
>               "args"=>{:content=>"None\n"}},
>              {"type"=>"ChildListingComponent",
>               "title"=>"Current Targets for the Audit Objective:"}]}]
>     File.open("nizam.yaml", "w"){|f| YAML.dump(convert_yaml.to_yaml, f)}

In your previous report, you receive this error:

C:/Users/Hekmatyer/Documents/NetBeansProjects/Nizam_BARU/lib/Environmental.rb:167:in
`[]': can't convert String into Integer (TypeError)

Without knowing how line 167 in Environment.rb relates to the code
snippets in question it's hard to tell where the problem might be.  My
guess is that the problem lies in the second line (pp convert_yaml[...)
from each snippet.

First of all, try commenting that out and see if your problem goes away.
 If it does, then the problem is likely that you're attempting to use a
string to index into an array when you intend to lookup in a hash.  In
other words, the content of convert_yaml has a different structure than
you expect in your code.  To further debug this, you should replace your
current pp line with the following lines:

convert_yaml["System"]
convert_yaml["System"]["Environmental"]
convert_yaml["System"]["Environmental"]["children"]
convert_yaml["System"]["Environmental"]["children"][2]["children"]

One of the above lines will reproduce the error, and you can use the
line number of the file listed in the error to identify which of the
statements is problematic.

-Jeremy

Hi Jeremy,

Thanks for the post. I am able to solve the problem and the error 
message disappear. Thank you

Nizam

Kamarulnizam Rahim wrote in post #977784:
> Hi Jeremy,
>
> Thanks for the post. I am able to solve the problem and the error
> message disappear. Thank you
>
> Nizam

Hi,

My question may not be exactly related to this question but quite 
similar. I am comparing two yaml files. The first one is my source file 
and the other one is my destination file. The source file contains KVs 
that do not exist in my destination file. I want those missing KVs to be 
written to my destination file. However, I do not want to simply add the 
missing KVs at the end of my destination file. I want to be able to 
insert them at the right position within hash hierarchy. So say my 
source file contains:
term:
  attributes:
    project: Project
    audit: Audit

and my destination file contains
term:
  attributes:
    project: Project

I want to write audit: Audit to my destination file considering its 
hierarchy.

Thanks
Marjan