About OpenAPIClientWizard

OpenAPIClientWizard – the ultimate plugin for RAD Studio that revolutionizes the way Delphi developers implement REST API clients.

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alidehbansiahkarbon

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OpenAPI Client Wizard

OpenAPI Client Wizard is a RAD Studio IDE plugin that generates Delphi REST API client projects from Swagger, OpenAPI, and Postman specifications.

No AI!

It is designed to remove the repetitive work of reading API documentation, translating every endpoint by hand, building request objects, wiring HTTP calls, and writing sample usage code. Give the wizard a supported specification and it generates a Delphi wrapper plus an optional ready-to-run sample project.

IDE Support

Delphi 10.1 Berlin through Delphi 12.x Athens
VCL project generation
Console project generation
Wrapper/SDK-only generation

Supported Inputs

Swagger 2.0 JSON
OpenAPI 3.x JSON
OpenAPI 3.x YAML, including both .yaml and .yml
Postman Collection JSON
Legacy Postman collections with a top-level requests array

Specifications can be loaded from an offline file or downloaded from a direct documentation URL.

Current Features

Generates a strongly named Delphi client unit: OpenAPIClient.pas
Generates a reusable HTTP transport unit: OpenAPITransport.pas
Generates methods for common REST verbs, including GET, POST, PUT, PATCH, DELETE, HEAD, OPTIONS, TRACE, and CONNECT
Generates request DTO classes for request bodies
Supports nested request objects and arrays
Resolves local schema references for request DTO generation
Handles common composed request schemas such as allOf, oneOf, and anyOf
Escapes Delphi reserved words in generated identifiers
Generates VCL sample usage code for all discovered API methods
Generates console sample usage code for all discovered API methods
Supports wrapper/SDK-only generation when no sample UI is needed
Supports optional Base URL entry
Extracts the default Base URL from Swagger/OpenAPI/Postman data when available
Uses Bearer authentication by default in generated clients
Supports Basic and no-auth generation paths where configured
Detects application/json, application/x-www-form-urlencoded, and multipart/form-data request bodies
Includes offline specification samples for regression testing and manual verification

Output Modes

The wizard can generate one of three project styles:

Mode	Description
VCL sample	Generates a VCL project with a polished sample form and usage code for the generated client.
Console sample	Generates a console app with sample calls for all discovered API methods.
Wrapper/SDK only	Generates only the reusable client and transport units.

Getting Started

Install or build the plugin package in RAD Studio.
Open RAD Studio.
Go to File > New > Other.
Select OpenAPI Client Project Wizard.

Wizard entry

Choose the specification format and source.
Select the project output type.
Optionally enter a Base URL. If it is left blank, the wizard attempts to extract it from the specification.
Click Create Client Project.

Wizard settings

The generated project includes a ready-to-use TOpenAPIClient class and sample code that demonstrates how to call the discovered API methods.

Generated project

Offline Specification Samples

The repository includes a Specification samples folder with small, focused files for testing generation across supported formats:

Swagger 2.0 JSON
OpenAPI 3 JSON
OpenAPI 3 YAML
OpenAPI 3 .yml
Postman Collection v2.1
Postman Collection v2.0
Legacy Postman v1-style collection

The expanded samples include nested request bodies so request DTO generation can be tested without relying on a live API.

Notes And Limitations

For URL-based loading, provide a direct URL to the raw specification file.
GitHub page URLs are not raw file URLs. Use the raw file link instead.
Multipart request bodies are detected and their content type is propagated, but full file-upload transport support is still being expanded.
Streaming responses such as text/event-stream are currently generated as raw response strings.
Response DTO generation is planned; generated client methods currently return raw response text.
Very complex polymorphic schemas may still need additional generation rules.

Example:

Not suitable:
https://github.com/adewg/ICAR/blob/ADE-1/url-schemes/reproductionURLScheme.json

Suitable:
https://raw.githubusercontent.com/adewg/ICAR/ADE-1/url-schemes/reproductionURLScheme.json

Demo Video

Watch a short demo on YouTube(click on the image below):

Dependencies

This plugin uses the Neslib YAML library for YAML parsing. The required source is included in this repository for convenience.

You can find the upstream project here:

https://github.com/neslib/Neslib.Json

Support

If OpenAPI Client Wizard saves you time, please consider giving the repository a star.

You can also support my work by buying me a coffee. This helps me continue developing this plugin and other Delphi tools such as ChatGPTWizard and EasyDBMigrator.

Direct Support

OpenAPI Client Wizard is provided as-is. If you need custom implementation work or direct support, contact me by email:

[email protected]

Contributing

Contributions are welcome. If you find a bug, have a sample specification that fails, or want to improve generation quality, please open an issue or submit a pull request.

Good contributions include:

Small reproducible specifications
Generated Delphi compile errors
OpenAPI/Postman edge cases
Transport improvements
Sample project polish
Documentation fixes

License

This project is licensed under the MIT License. See LICENSE for details.

Delphi

OpenAPIClientWizard