What is flow style in YAML?

Introduction

Flow style is a syntax used to describe data structures in the YAML language. It was introduced as an alternative to the more common block style, which involves arranging YAML elements into separate blocks based on their level in the hierarchy of data. In contrast, flow style uses a single line for each element and places them directly next to each other. This can make for a more concise and readable YAML, especially when dealing with simple data structures.

Basic syntax

Flow style is very similar to JSON. The flow style syntax begins with a left curly brace ({), followed by the data structure elements separated by commas (,). Each element must be on its own line, without any indentation. The last element must also be followed by a right curly brace (}).

Below is an example of a basic flow style YAML document:

{  element1,  element2, element3 }
A basic flow style YAML document

Flow style does not use indentation or whitespace to denote nesting, as block style does. This can make it difficult to read if it contains complex data structures. Below is an example of a complex flow style YAML document:

{ "key": "value", 
  "array": ["element1", "element2"], 
  "nested_object": { "subkey1": "subvalue1", "subkey2": "subvalue2" }
}

Flow style lets us write data in one line. We use commas to separate the data. The left curly brace marks the start of the data structure, and the right curly brace marks the ends of it. We can also nest data inside other data structures.

Benefits

As flow style is more concise than block style and produces cleaner code, it is often preferred by developers who need to write complex or lengthy data structures. Additionally, using the flow style can reduce the chances of errors due to indention, since there is no need to keep track of indentation levels.

Conclusion

Overall, flow style is a useful syntax for describing data structures in YAML. Whether we're working with simple or complex data, it can help make our code more readable and easier to understand by using a single line per element. However, it can also be more difficult to work with than block style if our data contains many nested elements or complex structures. Regardless, it is an important format for developers who work with YAML regularly.

Learn more about the syntax, data types, and various key concepts related to the YAML language through this mini course at Educative, Introduction to YAML.

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