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How to create a module?

Let's use a case study: we have the task of creating a module that, for each client, puts X-Frame-Options header

In general, the creation of a module can be divided into several stages:

  1. Create an empty module
  2. Add the necessary providers
  3. Include the module into the application

Create an empty module​

We create a basic module, to do this we create an empty class SecurityModule and connect the decorator Module which is required for modules and in which we will add integrations with the application.

import { Module } from '@tramvai/core';

@Module({
  providers: [],
})
export class SecurityModule {}

The module can already be plugged into the application, but it won't do anything.

Adding providers​

To do this we need to add providers in the providers field. We had the task to add the headers, for that we will use commandLineListTokens to perform actions for each client and we will use responseManager to which we can write the information about the headers.

import { Module, commandLineListTokens, RESPONSE_MANAGER_TOKEN, provide } from '@tramvai/core';

@Module({
  providers: [
    provide({
      provide: commandLineListTokens.resolvePageDeps,
      multi: true,
      useFactory: ({ responseManager }: { responseManager: typeof RESPONSE_MANAGER_TOKEN }) =>
        function securityHeader() {
          responseManager.setHeader('X-Frame-Options', 'sameorigin');
        },
      deps: {
        responseManager: RESPONSE_MANAGER_TOKEN,
      },
    }),
  ],
})
export class SecurityModule {}

We have implemented a new multi-provider that has dependencies and is created through useFactory

After plugging the module into the application, for each client the useFactory function will be executed first with the deps passed and then the securityHeader function will be called, in which we will write the data into the obtained dependency and thus fulfill our goal.

Include our new module in the application​

Now it remains to plug the module into the application so that it can add its implementation:

import { createApp } from '@tramvai/core';
import { SecurityModule } from '@tramvai/module-security';

createApp({
  modules: [SecurityModule],
});

We can add the module not only to the application, but also to another module. To do this, we need to pass in the imports block and then when the MyCommonModule is connected, the SecurityModule will also be automatically connected

import { Module } from '@tramvai/core';
import { SecurityModule } from '@tramvai/module-security';

@Module({
  imports: [SecurityModule],
  providers: [],
})
export class MyCommonModule {}

Summary​

A SecurityModule was created, which will be called for each client and will add the necessary headers