Yaml

YAML
====
-  text files or configuration files that are returned
in a particular format called YAML.

- All docker compose files and All ansible playbooks are configuration files
written in particular format Yaml.

Similar to XML or JSON

A yaml file is used to represent data, in this case configuration data.

Key value pairs - seperated by a colon.
----------------------------------------

Fruit: Apple
Vegetable: Carrot

etc.

YOU MUST Have a space following the colon differentiatiing the key and the value.

ARRAY/LISTS
-----------

Fruits:
- Orange   (The dash indicates it is an element of an array.)
- Apple
- Banana

Vegetable:
- Carrot
- Cauliglower
- Tomato

Dictionaries/Map
=============
 - a dictionary is a set of properties group together under an item.

Banana:
    Calories: 105
    Fat: 0.4 g
    Carbs: 27 g

You must have an equal number of spaces in front of the properties of a single item.
 - they are all aligned together - all aligned together.

SPACES in YAML
==============
You must have an equal number of spaces in front of the properties of a single item.
 - they are all aligned together.

> if you have an extra space,
the value becomes a property of the preceeding item, not the parent dictionary item.
i.e.
Banana:
    Calories: 105
      Fat: 0.4 g
      Carbs: 27 g
Fat becomes a property of Calories...

If you make a spacing error / mistake, you will receive an syntax error message that states:
  Mapping values are not allowed here.

Key Value/Dictionary/Lists
==========================
- You can have lists containing dictionaries containing lists

Fruits:
    - Banana           (Element of the list - array)
        Calories: 105  (dictionaries of nutrition info for each element of the list)
        Fat: 0.4 g
        Carbs: 27 g

    - Grape
        Calories: 62
        Fat: 0.3 g
        Carbs: 16 g


DICTIONARY vs LIST vs LIST of DICTIONARIES
==========================================

ALL XML , json, or yaml is used to represent data.

All objects have properties: Color, price, model, engine, etc.

To store data (different information or properties) about an object (car) we use a dictionary.
 - Defined in a key value format.


DICTIONARY
===========
You can further break down individual properties into dictionaries (sub dictionaries almost)

e.g.

Color: Blue
Model: Corvette
Engine: v8
Price: $20k

 - e.g. Can add a dictionary to one property in this case model.

Color: Blue
Model:
  Name: Corvette
  Year: 1955
Engine: v8
Price: $20k


LIST of strings  (array)
====
- a list of the same types of objects
i.e. store six different corvettes names based on color of car.

- Blue corvette
- Grey corvette
- Red corvette
- Green corvette
- Blue corvette
- Black corvette

LIST of dictionaries
====================

Expand each item in the array and replace each name with the dictionary we built earlier.

simple:

-   Color: Blue
    Model: Corvette
    Engine: v8
    Price: $20k

-   Color: Grey
    Model: Corvette
    Engine: v8
    Price: $22k

More complex List of dictionaries with sub dictionary items:
-   Color: Blue
    Model:
      Name: Corvette
      Year: 1955
    Engine: v8
    Price: $20k

-   Color: Grey
    Model:
      Name: Corvette
      Year: 1985
    Engine: v8
    Price: $22k

-   Color: Red
    Model:
      Name: Corvette
      Year: 1965
    Engine: v8
    Price: $21k

-   Color: Green
    Model:
      Name: Corvette
      Year: 1975
    Engine: v8
    Price: $24k

-   Color: Blue
    Model:
      Name: Corvette
      Year: 1959
    Engine: v8
    Price: $25k

NOTES:   Ordered verses Unordered items
------------------------------------------

  Dictionary is an unordered group of information
   - the properties appear in any order
  List is an ordered group of information

DICTIONARY
Banana:
    Calories: 105
    Fat: 0.4 g
    Carbs: 27 g

- is the same as-

Banana:
    Calories: 105
    Carbs: 27 g   (notice Carbs and Fats are in different order )
    Fat: 0.4 g

LIST
-----
 - ordered so the items must be in the sames order

Vegetable:
- Carrot
- Tomato
- Cauliglower

-is NOT the same as

Vegetable:
- Carrot
- Cauliglower  (inverted order of items in the array.)
- Tomato

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