Syntax for empty dictionary in YAML

Question

How do I denote an empty dictionary in YAML? I.e. it should be semantically equivalent to the empty json-object {}.

Answer 1

Short answer: use {}

There are two ways to denote mappings (dictionaries) in yaml; flow mappings and block mappings:

block_mapping:     name:  foo     id:    bar flow_mapping: { name: foo, id: bar } empty_flow_mapping: {} 

The flow mapping style is thus suitable for representing empty mappings.

Answer 2

General technique for answering this type of question, to supplement Betamos’s correct answer: use irb.

$ irb 2.2.0 :001 > require 'yaml'  => true  2.2.0 :002 > puts({}.to_yaml)   # original question --- {}  => nil  2.2.0 :003 > puts({ mixed_types: [{}, "string", :symbol, {symbol: "value"}, nil, 3] }.to_yaml) --- :mixed_types: - {} - string - :symbol - :symbol: value -  - 3  => nil 

I use this whenever I’m unsure how to encode something.