YAML Basics

Posted by rachel2004 on Sun, 09 Jan 2022 05:59:34 +0100

From rookie tutorial, original address: https://www.runoob.com/w3cnote/yaml-intro.html


  • It is especially suitable for expressing or editing data structures, various configuration files, dump debugging contents and file outline
  • The configuration file suffix of YAML is YML, such as runoob yml 

Basic grammar

  • Case sensitive (Boolean values are case sensitive)
  • Use indents to identify hierarchical relationships
  • tap is not allowed for indentation, only spaces are allowed
  • The number of indented spaces is not important, as long as the elements of the same level are aligned to the left
  • #Identification notes

data type

📖 Object: a collection of key value pairs, also known as mapping / hashes / dictionary

Object key value pairs are represented by a colon structure, and a space should be added after the colon.

You can also use key:{key1: value1, key2: value2,...}.

You can also use indentation to represent hierarchical relationships;

    child-key: value
    child-key2: value2

For more complex object formats, you can use a question mark plus a space to represent a complex key, and a colon plus a space to represent a value:

    - complexkey1
    - complexkey2
    - complexvalue1
    - complexvalue2

That is, the attribute of the object is an array [complexkey1,complexkey2], and the corresponding value is also an array [complexvalue1,complexvalue2]


📖 Array: a set of values arranged in order, also known as sequence / list

Lines beginning with - form an array:

- A
- B
- C

YAML supports multi-dimensional arrays and can use inline representation:

key: [value1, value2, ...]

If the child member of the data structure is an array, you can indent a space under the item.

 - A
 - B
 - C

A relatively complex example:

        id: 1
        name: company1
        price: 200W
        id: 2
        name: company2
        price: 500W

It means that the companies attribute is an array, and each array element is composed of three attributes: id, name and price.

Arrays can also be expressed in flow:

companies: [{id: 1,name: company1,price: 200W},{id: 2,name: company2,price: 500W}]


📖 Composite structure

Arrays and objects can form a composite structure, for example:

  - Ruby
  - Perl
  - Python 
  YAML: yaml.org 
  Ruby: ruby-lang.org 
  Python: python.org 
  Perl: use.perl.org

Convert to json:

  languages: [ 'Ruby', 'Perl', 'Python'],
  websites: {
    YAML: 'yaml.org',
    Ruby: 'ruby-lang.org',
    Python: 'python.org',
    Perl: 'use.perl.org' 


📖 scalars: single, non separable values

Scalar is the most basic and non separable value, including:

  • character string
  • Boolean value
  • integer
  • Floating point number
  • Null
  • time
  • date

Use an example to quickly understand the basic use of scalars:

    - TRUE  #true,True is OK
    - FALSE  #False, false is OK
    - 3.14
    - 6.8523015e+5  #Scientific counting can be used
    - 123
    - 0b1010_0111_0100_1010_1110    #Binary representation
    nodeName: 'node'
    parent: ~  #Use ~ for null
    - ha-ha
    - 'Hello world'  #You can wrap special characters in double quotation marks or single quotation marks
    - newline
      newline2    #The string can be split into multiple lines, and each line will be converted into a space
    - 2018-02-17    #The date must be in ISO 8601 format, i.e. yyyy mm DD
    -  2018-02-17T15:02:31+08:00    #The time is in ISO 8601 format, the T connection is used between the time and date, and the last + is used to represent the time zone


📖 quote

&Anchor point and * alias, which can be used to refer to:

defaults: &defaults
  adapter:  postgres
  host:     localhost

  database: myapp_development
  <<: *defaults

  database: myapp_test
  <<: *defaults

amount to:

  adapter:  postgres
  host:     localhost

  database: myapp_development
  adapter:  postgres
  host:     localhost

  database: myapp_test
  adapter:  postgres
  host:     localhost

&It is used to establish anchors, < < means merging into the current data, * is used to reference anchors.

Here is another example:

- &showell Steve 
- Clark 
- Brian 
- Oren 
- *showell 

The code to JavaScript is as follows:

[ 'Steve', 'Clark', 'Brian', 'Oren', 'Steve' ]


Topics: yaml