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Angular–Generate your OpenAPI client model

Most Angular applications need some kind of data typically provided through an OpenAPI or GraphQL API. Manually creating all the necessary model classes and client can be a time-consuming and error-prone task. In this post we have a look at ng-openapi-gen to help you automate this process.

We start by installing the ng-openapi-gen module by executing the following command:

npm install -g ng-openapi-gen

Now we can generate our models and web client in the Angular application using the following command:

ng-openapi-gen --input <path-to-openapi-json> --output <angular-app-path>/src/app/shared/api

If you look at the command above you see that it requires to an OpenAPI specification file. This can be in JSON or YAML format. So we first need a way to get this specification file.

If you are using ASP.NET Core with the OpenAPI integration, you can either download the OpenAPI file manually by going to the swagger UI and download it there or you can generate the OpenAPI file at build time as I explained in a previous post.

Once you have an OpenAPI file available, we can now execute the command:

ng-openapi-gen --input ../Swashbuckle/api.json --output src/app/shared/api

Let's have a look at what is generated:

  • For every DTO a model class is generated in the models subfolder;
  • For each tag in our OpenAPI specification an Angular @Injectable() service is generated in the services subfolder;
  • An Angular @NgModule() is generated , which provides all services, together with some base classes could be found in the root folder;


Great! Now before we can use these generated module, we need to update our AppModule to import the generated ApiModule and configure the root URL:

Finally we can import and use the generated client in our Angular components or if we are using NgRx in our effects:

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