Cool Yaml Features You Probably Didn’t Know About

Anchors

man:
  name: Utibe
  age: 1000
  galaxy: milky-way
  dinosaursExist: no
alien:
  name: kal-el
  age: 10000000
  galaxy: milky-way
  dinosaursExist: no
names:
  - Utibe
  - kal-el

As you can see, we have a names key that lists the names of both man and alien. However, this is not ideal as we are writing out the names multiple times and if the name changes we have to change each reference to it. YAML has a feature known as anchors that allows us to reference a value. Here’s how it works

man:
  name: &man Utibe
  age: 1000
  galaxy: milky-way
  dinosaursExist: no
alien:
  name: &alien kal-el
  age: 10000000
  galaxy: milky-way
  dinosaursExist: no
names:
  - *man
  - *alien

Remove Redundancy With Anchors

metadata: &metadata
  galaxy: milky-way
  dinosaursExist: no
man:
  name: &man Utibe
  age: 1000
  <<: *metadata
alien:
  name: &alien kal-el
  age: 10000000
  <<: *metadata
names:
  - *man
  - *alien

And to overide standard template metadata in this example with specific values simply overwrite at the end as if the last thing read is what happens like in CSS

man:
  name: &man Utibe
  age: 1000
  <<: *metadata
  galaxy: another-galaxy

Explicit Tags

For data type casting

numbers:
    num1: !!int 1.0 # converted to 1
    num2: !!float 100 # converted to 100.0
    num3: !!str 150 # converted to "150"

Multi-line strings

Literal Block

This preserves the \n character at the end of each line, such as in a list of executed CLI commands

script: |
    echo "hello world" > file.txt
    cat file.txt
    sed s/hello/Hello/g file.txt > file2.txt
    mv file2.txt file.txt

Folded Block Approach

This treats the text as a single run on sentance with no new lines akin to:

script: Hello there This is some text but will be on the same line as the previous text

script: >
    Hello there
    This is some text
    but will be on the same line as the previous text

Multiple YAML Docs in a single file

In YAML the compile sees --- as a separator between 2 different YAML documents

name: "File one"
age: "one day"
planet: "earth"
---
name: "File two"
age: "two billion light years"
planet: "Jupiter"