Newbie Rubyist wants to get the concept of YAML

Ruby
1

I am reading ‘Learning to Code’ by Chris P…

One section talks about Yaml. In Chris’s code, he always puts a test at
the end (e.g. ‘puts(read_array == test_array)’ ) I am wondering what it
does! Thanks!!

The attached screenshot is the complete script he used as an example.

THANKS!!

2

So, this example doesn’t have much to do about YAML, except that YAML is
a way to serialize an object, much like Marshal.

What the example demonstrates is that you can serialize and deserialize
an Array to/from a file.

try this from your command line

ruby -ryaml -e ‘puts YAML::dump %w[a b c]’
and then
ruby -ryaml -e ‘yaml = YAML::dump( %w[a b c] ); p YAML::load(yaml)’

3

Benjamin F. wrote in post #1166359:

So, this example doesn’t have much to do about YAML, except that YAML is
a way to serialize an object, much like Marshal.

What the example demonstrates is that you can serialize and deserialize
an Array to/from a file.

try this from your command line

ruby -ryaml -e ‘puts YAML::dump %w[a b c]’
and then
ruby -ryaml -e ‘yaml = YAML::dump( %w[a b c] ); p YAML::load(yaml)’

Thank you for your response Benjamin!

But I am sorry if I sound dumb…I have never come across anything like
the two lines above…what exactly do they do?? Thanks in advance!!

4

It a ruby program that you can type in and run entirely from the command
line. No need to save it in a file and run it from a file.

ruby --help

-rlibrary require the library before executing your script

-ryaml loads the yaml library. It’s the equivalent of the require ‘yaml’
line in the Pine example.

-e ‘command’ one line of script. Several -e’s allowed.

The program code then follows in single quotes following the -e.

‘puts YAML::dump %w[a b c]’

For that line of code try reading it from right to left.

%w[a b c] create an array containing three characters. It’s a shortcut
way of typing [‘a’, ‘b’, ‘c’]. Open up irb and try it:

C:\Users\Scott>irb --simple-prompt

%w[a b c]
=> [“a”, “b”, “c”]

exit

dump is a method in the yaml library. Your passing in the array to that
method. YAML::dump(%w[a b c])

puts just sends the output to the console rather than to a file. But
what you see is the contents of the array in the YAML format. You can
look up more about YAML online.

Here’s the whole thing in irb:

C:\Users\Scott>irb --simple-prompt

require ‘yaml’
=> true

puts YAML::dump %w[a b c]

  • a
  • b
  • c
    => nil

exit