JSON to Crystal Class Converter

JSON to Crystal Class: Core Features and Principles

When you need to convert JSON API responses or configuration data into type-safe classes in the Crystal language, manually writing field mappings and type declarations is both tedious and error-prone. This tool parses your input JSON string, automatically infers field types and nested structures, and generates Crystal class or struct code with JSON::Serializable support. The core processing object is a JSON-compliant data structure, and the output is Crystal class definition code that can be directly embedded into your project.

Why Choose Our JSON to Crystal Class Converter?

• Smart type inference: Automatically matches JSON values to Crystal types like Int32, String, Bool, and Array, reducing manual declaration errors.
• Automatic naming convention conversion: Converts common JSON camelCase field names into Crystal's idiomatic snake_case property names, adhering to language standards.
• Comprehensive nested object handling: Recursively parses multi-level JSON objects, generating independent class definitions for each nested level to maintain structural integrity.

Tutorial

1. Paste a valid JSON string into the input box.
2. Click the "Generate Crystal Class" button to execute the conversion.
3. Copy the generated Crystal class code from the output area into your project.

FAQ:

How does the JSON to Crystal converter handle null fields?
The tool infers null values in JSON as the Nil type, generating nullable type declarations like property name : String? to ensure type safety.

What if the input JSON format is invalid?
The system will prompt a JSON parsing error and abort the conversion. Please use an online JSON validator to check the validity of your data format first.

Notes

Please ensure the input is in standard JSON format. Complex nested structures may require manual adjustments to the generated type annotations. The generated code does not include custom method logic, which developers will need to add based on business requirements. All processing is done locally in your browser; your JSON data is never sent to a server.

Technical Notes & Tips

For scenarios requiring precise control over serialization behavior, we recommend manually adding JSON::Field annotations after generating the code. For example, use @[JSON::Field(key: "originalName")] to maintain the mapping with the original JSON field. Typical input/output example: Inputting {"userName":"Alice","age":25} will generate the class definitions property user_name : String and property age : Int32.