Ruby on Rails中如何正确返回含关联Tag的用户JSON数据

The issue you're facing is due to double JSON serialization: when you call to_json on the users collection first, you convert it into a string. Then when you pass that string into the response hash and call render json: response, Rails serializes the entire hash again—turning your already-formatted JSON string into an escaped string within the final JSON output.

Here are two clean solutions to fix this and get your desired nested Tag structure:

Solution 1: Use as_json instead of to_json #

as_json converts ActiveRecord objects into a Ruby hash/array structure (not a JSON string), which can then be safely included in your response hash without escaping. Combine this with eager loading to avoid N+1 database queries:

# Eager load tags to optimize performance (avoids N+1 queries)
users = User.where(some_condition).includes(:tag)
# Convert users to a Ruby hash with nested tag data
users_with_tags = users.as_json(include: :tag)
# Build your response hash with the structured data
response = { token: current_user.token, users: users_with_tags }
# Render the entire hash as JSON (no double serialization)
render json: response

Solution 2: Pass Serialization Options Directly to render #

Keep your users as ActiveRecord objects, and tell Rails to include the Tag association when rendering the final JSON. This is more concise and leverages Rails' built-in serialization:

# Eager load tags for performance
users = User.where(some_condition).includes(:tag)
response = { token: current_user.token, users: users }
# Specify nested includes to serialize tags with each user
render json: response, include: { users: { include: :tag } }

Both approaches will produce your desired JSON format without escaped characters:

{
  "token": "token_value",
  "users": [
    {
      "id": 377,
      "nome": "CAIXA-ALM-CPARK-PE-ELE-0203-PAV00-nomeDoarquivo.dwg",
      // ... other user fields
      "tag": {
        "id":7,
        "nome":"ELÉTRICA",
        "cor":"#4A148C",
        // ... other tag fields
      }
    }
  ]
}

Content of this question originates from Stack Exchange, asked by Lucas Andrade