How to Read JSON in Ruby: Simple Guide with Examples

To read JSON in Ruby, use the JSON.parse method from the built-in json library. First, require the library with require 'json', then call JSON.parse(json_string) to convert a JSON string into a Ruby hash or array.

Syntax

To read JSON in Ruby, you need to:

• Require the JSON library: require 'json'
• Parse the JSON string: Use JSON.parse(json_string) to convert JSON text into Ruby data structures like hashes or arrays.

ruby

require 'json'

ruby_object = JSON.parse(json_string)

Example

This example shows how to read a JSON string and access its data as a Ruby hash.

ruby

require 'json'

json_string = '{"name": "Alice", "age": 30, "languages": ["Ruby", "Python"]}'

ruby_hash = JSON.parse(json_string)

puts "Name: #{ruby_hash['name']}"
puts "Age: #{ruby_hash['age']}"
puts "Languages: #{ruby_hash['languages'].join(', ')}"

Output

Name: Alice
Age: 30
Languages: Ruby, Python

Common Pitfalls

Common mistakes when reading JSON in Ruby include:

• Forgetting to require 'json', which causes NameError.
• Trying to parse invalid JSON strings, which raises JSON::ParserError.
• Accessing keys with symbols instead of strings, since JSON.parse returns keys as strings by default.

To avoid symbol key issues, you can use JSON.parse(json_string, symbolize_names: true) to get symbol keys.

ruby

require 'json'

json_string = '{"key": "value"}'

# Wrong: keys are strings, not symbols
ruby_hash = JSON.parse(json_string)
puts ruby_hash[:key] # => nil

# Right: use symbolize_names option
ruby_hash_sym = JSON.parse(json_string, symbolize_names: true)
puts ruby_hash_sym[:key] # => "value"

Output

nil
value

Quick Reference

Action	Code Example
Require JSON library	require 'json'
Parse JSON string	JSON.parse(json_string)
Parse with symbol keys	JSON.parse(json_string, symbolize_names: true)
Handle parse errors	begin JSON.parse(bad_json) rescue JSON::ParserError => e puts "Invalid JSON: #{e.message}" end

Key Takeaways

Always require the 'json' library before parsing JSON in Ruby.

Use JSON.parse to convert JSON strings into Ruby hashes or arrays.

By default, keys are strings; use symbolize_names: true to get symbol keys.

Handle JSON::ParserError to catch invalid JSON data gracefully.

Access parsed data using string or symbol keys depending on parsing options.