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Resolvers

Defining the Resolver​

Auto Generated Resolver​

The easiest way to get started is to use the @NestjsQueryGraphQLModule. The NestjsQueryGraphQLModule will automatically create a CRUDResolver for you.

todo-item.module.ts
import { NestjsQueryGraphQLModule } from '@ptc-org/nestjs-query-graphql';
import { NestjsQueryTypeOrmModule } from '@ptc-org/nestjs-query-typeorm';
import { Module } from '@nestjs/common';
import { TodoItemDTO } from './todo-item.dto';
import { TodoItemEntity } from './todo-item.entity';

@Module({
  imports: [
    NestjsQueryGraphQLModule.forFeature({
      imports: [NestjsQueryTypeOrmModule.forFeature([TodoItemEntity])],
      resolvers: [{ DTOClass: TodoItemDTO, EntityClass: TodoItemEntity }],
    }),
  ],
})
export class TodoItemModule {}

CRUDResolver​

If you want to override auto generated queries or mutations you can use the CRUDResolver to manually define your resolver.

Resolvers work the same as they do in @nestjs/graphql by annotating your class with @Resolver.

note

In this example the DTO and entity are the same shape, if you have a case where they are different or have computed fields check out Assemblers to understand how to convert to and from the DTO/Entity.

warning

When using the @Resolver decorator from @nestjs/graphql you must use the following

@Resolver(() => DTOClass)

otherwise relations will not work.

todo-item.resolver.ts
import { QueryService, InjectQueryService } from '@ptc-org/nestjs-query-core';
import { CRUDResolver } from '@ptc-org/nestjs-query-graphql';
import { Resolver, Query, Args } from '@nestjs/graphql';
import { TodoItemDTO } from './dto/todo-item.dto';
import { TodoItemEntity } from './todo-item.entity';

@Resolver(() => TodoItemDTO)
export class TodoItemResolver extends CRUDResolver(TodoItemDTO) {
  constructor(
    @InjectQueryService(TodoItemEntity) readonly service: QueryService<TodoItemEntity>
  ) {
    super(service);
  }
}

To ensure that all the correct providers are setup (e.g. hooks, assemblers, and authorizers) you also need to register your DTOs with the NestjsQueryGraphQLModule.

Notice how the dtos property is specified instead of the resolvers, this allows you to specify your DTOClass, CreateDTOClass, and UpdateDTOClass without creating an auto-generated resolver.

todo-item.module.ts
import { NestjsQueryGraphQLModule } from '@ptc-org/nestjs-query-graphql';
import { NestjsQueryTypeOrmModule } from '@ptc-org/nestjs-query-typeorm';
import { Module } from '@nestjs/common';
import { TodoItemDTO } from './todo-item.dto';
import { TodoItemEntity } from './todo-item.entity';
import { TodoItemResolver } from './todo-item.resolver'

@Module({
  providers: [TodoItemResolver]
  imports: [
    NestjsQueryGraphQLModule.forFeature({
      imports: [NestjsQueryTypeOrmModule.forFeature([TodoItemEntity])],
      dtos: [{ DTOClass: TodoItemDTO }],
    }),
  ],
})
export class TodoItemModule {}
warning

All of the subsequent examples omit the module definition for custom resolvers but you should still register your DTOs to ensure all the providers are set up properly.

Generated Endpoints​

When using the auto-generated resolver or extending CRUDResolver the methods that will be exposed for the TodoItemDTO are:

  • todoItem - Find a single TodoItem by id.
  • todoItems - Filter, sort, and page TodoItems
  • createOneTodoItem - Create a single TodoItem
  • createManyTodoItems - Create multiple TodoItems.
  • updateOneTodoItem - Update a single TodoItem by id.
  • updateManyTodoItems - Update multiple TodoItems using a filter.
  • deleteOneTodoItem - Delete a single TodoItem by id.
  • deleteManyTodoItems - Delete multiple TodoItems using a filter.

You can read more about the methods in the Queries and Mutations docs.

Options​

When using NestjsQueryGraphQLModule or CRUDResolver you can define a number of options to control your endpoints.

  • CreateDTOClass - The input DTO to use for create mutations. See Create and Update DTOs

  • UpdateDTOClass - The input DTO to use for update mutations. See Create and Update DTOs

  • enableSubscriptions? - Set to true to enable graphql subscriptions. See Subscriptions.

  • enableAggregate? - When set to true an aggregate query will be enabled on the type and all relations (unless the explicitly disable it). See Aggregation

  • create - In addition to ResolverOptions you can also specify the following

    • CreateDTOClass - The input DTO to use for create mutations.
    • CreateOneInput - The InputType to use for create one mutations.
    • CreateManyInput - The InputType to use for create many mutations.

  • read - In addition to ResolverOptions you can also specify the following

    • QueryArgs - Specify to override the auto-generated ArgsType to use to filter records in queryMany endpoint.

  • update - In addition to ResolverOptions you can also specify the following

    • UpdateDTOClass - The input DTO to use for update mutations.
    • UpdateOneInput - The InputType to use for update one mutations.
    • UpdateManyInput - The InputType to use for update many mutations.

  • delete - In addition to ResolverOptions you can also specify the following

    • DeleteOneInput - The InputType to use for delete one mutations.
    • DeleteManyInput - The InputType to use for delete many mutations.

  • aggregate - In addition to ResolverOptions you can also specify the following

    • enabled - Set to true to enable aggregations. If this is used in place of the root enableAggregate option relations will not have aggregate queries exposed.

ResolverOptions​

The create, read, update, and delete options above all accept the following options.

  • dtoName - Set to override the default name (the name passed to @ObjectType or the name of the class).
  • disabled=false - Set to true to disable all endpoints.
  • guards=[] - An array of guards to add to all endpoints.
  • interceptors=[] - An array of interceptors to add to all endpoints.
  • pipes=[] - An array of pipes to add to all endpoints.
  • filters=[] - An array of filters to add to all endpoints.
  • decorators=[] - An array of custom PropertyDecorator or MethodDecorators to add to the endpoint.
  • enableSubscriptions? - Set to true to enable graphql subscriptions. See Subscriptions.
  • one, many - Both the one and many accept the following options:
    • name? - Override the endpoint name.
    • disabled=false - Set to true to disable the endpoint.
    • enableSubscriptions? - Set to true to enable graphql subscriptions. See Subscriptions.
    • guards=[] - An array of guards to add to the endpoint.
    • interceptors=[] - An array of interceptors to add to the endpoint.
    • pipes=[] - An array of pipes to add to the endpoint.
    • filters=[] - An array of filters to add to the endpoint.
    • decorators=[] - An array of custom PropertyDecorator or MethodDecorators to add to the endpoint.

Examples​

Create and Update DTOs.​

There may be times when you want to specify certain validation or only allow certain fields when updating or creating records.

To allow for this you can specify the CreateDTOClass and UpdateDTOClass options.

Example​

In this example we'll create a new TodoItemInputDTO that adds validation and limits the fields you can modify.

Assume we have the following class todo-item.input.ts which omits the id, created, and updated fields from the original DTO.

todo-item.input.ts
import { Field, InputType } from '@nestjs/graphql';
import { IsString, Length } from 'class-validator';

@InputType('TodoItemInput')
export class TodoItemInputDTO {
  @Field()
  // ensure it is a string field
  @IsString()
  // min length of 5 and max of 5 characters
  @Length(5, 50)
  title!: string;

  @Field()
  completed!: boolean;
}

We can then update our resolver to use the new TodoItemInputDTO

todo-item.module.ts
import { NestjsQueryGraphQLModule } from '@ptc-org/nestjs-query-graphql';
import { NestjsQueryTypeOrmModule } from '@ptc-org/nestjs-query-typeorm';
import { Module } from '@nestjs/common';
import { TodoItemInputDTO } from './todo-item.input';
import { TodoItemDTO } from './todo-item.dto';
import { TodoItemEntity } from './todo-item.entity';

@Module({
  imports: [
    NestjsQueryGraphQLModule.forFeature({
      imports: [NestjsQueryTypeOrmModule.forFeature([TodoItemEntity])],
      resolvers: [{
        DTOClass: TodoItemDTO,
        EntityClass: TodoItemEntity,
        CreateDTOClass: TodoItemInputDTO,
        UpdateDTOClass: TodoItemInputDTO,
      }],
    }),
  ],
})
export class TodoItemModule {}

Disabling Endpoints.​

There may be scenarios where you wish to disable certain methods.

Using the options describe above we can disable different actions.

In this example we disable all create endpoints

todo-item.module.ts
import { NestjsQueryGraphQLModule } from '@ptc-org/nestjs-query-graphql';
import { NestjsQueryTypeOrmModule } from '@ptc-org/nestjs-query-typeorm';
import { Module } from '@nestjs/common';
import { TodoItemDTO } from './todo-item.dto';
import { TodoItemEntity } from './todo-item.entity';

@Module({
  imports: [
    NestjsQueryGraphQLModule.forFeature({
      imports: [NestjsQueryTypeOrmModule.forFeature([TodoItemEntity])],
      resolvers: [{
        DTOClass: TodoItemDTO,
        EntityClass: TodoItemEntity,
        create: { disabled: true }
      }],
    }),
  ],
})
export class TodoItemModule {}

You can also disable individual endpoints.

In this example we disable all many mutations. This will prevent createManyTodoItems, updateManyTodoItems, deleteManyTodoItems from being exposed in the graphql schema.

NOTE The same pattern applies for disabling the one endpoints.

todo-item.module.ts
import { NestjsQueryGraphQLModule } from '@ptc-org/nestjs-query-graphql';
import { NestjsQueryTypeOrmModule } from '@ptc-org/nestjs-query-typeorm';
import { Module } from '@nestjs/common';
import { TodoItemDTO } from './todo-item.dto';
import { TodoItemEntity } from './todo-item.entity';

@Module({
  imports: [
    NestjsQueryGraphQLModule.forFeature({
      imports: [NestjsQueryTypeOrmModule.forFeature([TodoItemEntity])],
      resolvers: [{
        DTOClass: TodoItemDTO,
        EntityClass: TodoItemEntity,
        create: { many: { disabled: true } },
        update: { many: { disabled: true } },
        delete: { many: { disabled: true } },
      }],
    }),
  ],
})
export class TodoItemModule {}

Guards, Pipes, Filters, and Interceptors​

In this section we'll just demonstrate using a guard but the same pattern applies for pipes, filters and interceptors

To set up a guard for endpoint you can use the guards option.

Assume we have the following auth guard that checks for a certain header and value.

auth.guard.ts
import {
  CanActivate,
  ExecutionContext,
  Injectable,
  Logger,
} from '@nestjs/common';
import { Observable } from 'rxjs';
import { GqlExecutionContext } from '@nestjs/graphql';
import { AUTH_HEADER_NAME } from './constants';
import { config } from './config';

@Injectable()
export class AuthGuard implements CanActivate {
  private logger = new Logger(AuthGuard.name);

  canActivate(
    context: ExecutionContext,
  ): boolean | Promise<boolean> | Observable<boolean> {
    const ctx = GqlExecutionContext.create(context);
    const req = ctx.getContext().request;
    this.logger.log(`Req = ${req.headers}`);
    return req.headers[AUTH_HEADER_NAME] === config.auth.header;
  }
}

We can then add it to each of our mutation endpoints

todo-item.module.ts
import { NestjsQueryGraphQLModule } from '@ptc-org/nestjs-query-graphql';
import { NestjsQueryTypeOrmModule } from '@ptc-org/nestjs-query-typeorm';
import { Module } from '@nestjs/common';
import { AuthGuard } from '../auth.guard';
import { TodoItemDTO } from './todo-item.dto';
import { TodoItemEntity } from './todo-item.entity';

const guards = [AuthGuard];

@Module({
  imports: [
    NestjsQueryGraphQLModule.forFeature({
      imports: [NestjsQueryTypeOrmModule.forFeature([TodoItemEntity])],
      resolvers: [{
        DTOClass: TodoItemDTO,
        EntityClass: TodoItemEntity,
        create: { guards },
        update: { guards },
        delete: { guards },
      }],
    }),
  ],
})
export class TodoItemModule {}

Now any requests that go to a create, update or delete method will require the guard.

You can also apply to individual methods using the one and many fields. For example lets put a guard on all many mutations.

todo-item.module.ts
import { NestjsQueryGraphQLModule } from '@ptc-org/nestjs-query-graphql';
import { NestjsQueryTypeOrmModule } from '@ptc-org/nestjs-query-typeorm';
import { Module } from '@nestjs/common';
import { AuthGuard } from '../auth.guard';
import { TodoItemDTO } from './todo-item.dto';
import { TodoItemEntity } from './todo-item.entity';

const guards = [AuthGuard];

@Module({
  imports: [
    NestjsQueryGraphQLModule.forFeature({
      imports: [NestjsQueryTypeOrmModule.forFeature([TodoItemEntity])],
      resolvers: [{
        DTOClass: TodoItemDTO,
        EntityClass: TodoItemEntity,
        create: { many: { guards } },
        update: { many: { guards } },
        delete: { many: { guards } },
      }],
    }),
  ],
})
export class TodoItemModule {}

Override Endpoint Name​

If you find yourself in a situation where you want to override an endpoint name you can use the one.name or many.name options to override

note

These options are available for the create, read, update, and 'delete' endpoints.

In this example we'll change the todoItem query to findTodoItem and the todoItems endpoint to queryForTodoItems.

todo-item.module.ts
import { NestjsQueryGraphQLModule } from '@ptc-org/nestjs-query-graphql';
import { NestjsQueryTypeOrmModule } from '@ptc-org/nestjs-query-typeorm';
import { Module } from '@nestjs/common';
import { TodoItemDTO } from './todo-item.dto';
import { TodoItemEntity } from './todo-item.entity';

@Module({
  imports: [
    NestjsQueryGraphQLModule.forFeature({
      imports: [NestjsQueryTypeOrmModule.forFeature([TodoItemEntity])],
      resolvers: [{
        DTOClass: TodoItemDTO,
        EntityClass: TodoItemEntity,
        read: { one: { name: 'findTodoItem' }, many: { name: 'queryForTodoItems' } },
      }],
    }),
  ],
})
export class TodoItemModule {}

Individual Resolvers​

The @ptc-org/nestjs-query-graphql package exposes each part of CRUD into individual mixins and resolvers allowing you to pick and choose what functionality you want to expose.

note

This is advanced usage of the resolvers API and is subject to change!

  • All examples below can be achieved with resolver options.
  • The following resolvers do not expose relations options, to add relations options see Relateable

CreateResolver​

The CreateResolver will only expose the createOne and createMany endpoints. The options described for create can be passed to the CreateResolver

For example the following resolver will expose the createOneTodoItem and createManyTodoItems mutations.

todo-item.resolver.ts
import { QueryService, InjectQueryService } from '@ptc-org/nestjs-query-core';
import { CreateResolver } from '@ptc-org/nestjs-query-graphql';
import { Resolver } from '@nestjs/graphql';
import { TodoItemDTO } from './todo-item.dto';
import { TodoItemEntity } from './todo-item.entity';

@Resolver()
export class TodoItemResolver extends CreateResolver(TodoItemDTO) {
  constructor(
      @InjectQueryService(TodoItemEntity) readonly service: QueryService<TodoItemEntity>
  ) {
    super(service);
  }
}

ReadResolver​

The ReadResolver will only expose the query and findById endpoints. The options described for read can be passed to the ReadResolver

For example the following resolver will expose the todoItems and todoItem queries.

todo-item.resolver.ts
import { QueryService, InjectQueryService } from '@ptc-org/nestjs-query-core';
import { ReadResolver } from '@ptc-org/nestjs-query-graphql';
import { Resolver } from '@nestjs/graphql';
import { TodoItemDTO } from './todo-item.dto';
import { TodoItemEntity } from './todo-item.entity';

@Resolver()
export class TodoItemResolver extends ReadResolver(TodoItemDTO) {
  constructor(
    @InjectQueryService(TodoItemEntity) readonly service: QueryService<TodoItemEntity>
  ) {
    super(service);
  }
}

UpdateResolver​

The UpdateResolver will only expose the updateOne and updateMany endpoints. The options described for update can be passed to the UpdateResolver

For example the following resolver will expose the updateOneTodoItem and updateManyTodoItems mutations.

todo-item.resolver.ts
import { QueryService, InjectQueryService } from '@ptc-org/nestjs-query-core';
import { UpdateResolver } from '@ptc-org/nestjs-query-graphql';
import { Resolver } from '@nestjs/graphql';
import { TodoItemDTO } from './todo-item.dto';
import { TodoItemEntity } from './todo-item.entity';

@Resolver()
export class TodoItemResolver extends UpdateResolver(TodoItemDTO) {
  constructor(
    @InjectQueryService(TodoItemEntity) readonly service: QueryService<TodoItemEntity>
  ) {
    super(service);
  }
}

DeleteResolver​

The DeleteResolver will only expose the deleteOne and deleteMany endpoints. The options described for delete can be passed to the DeleteResolver

For example the following resolver will expose the updateOneTodoItem and updateManyTodoItems mutations.

todo-item.resolver.ts
import { QueryService, InjectQueryService } from '@ptc-org/nestjs-query-core';
import { DeleteResolver } from '@ptc-org/nestjs-query-graphql';
import { Resolver } from '@nestjs/graphql';
import { TodoItemDTO } from './todo-item.dto';
import { TodoItemEntity } from './todo-item.entity';

@Resolver()
export class TodoItemResolver extends DeleteResolver(TodoItemDTO) {
  constructor(
    @InjectQueryService(TodoItemEntity) readonly service: QueryService<TodoItemEntity>
  ) {
    super(service);
  }
}

Custom Endpoints​

You can also create custom methods.

note

Unless you are overriding an endpoint you DO NOT need to extend the crud resolver directly, instead you can create a new resolver for your type and add the new endpoint. @nestjs/graphql will handle merging the two resolver into one.

Lets create a new query endpoint that only returns completed TodoItems.

First create a file named types.ts. And add the following.

types.ts
import { QueryArgsType } from '@ptc-org/nestjs-query-graphql';
import { ArgsType } from '@nestjs/graphql';
import { TodoItemDTO } from './dto/todo-item.dto';


@ArgsType()
export class TodoItemQuery extends QueryArgsType(TodoItemDTO) {}
export const TodoItemConnection = TodoItemQuery.ConnectionType;

In the code above we export two types. TodoItemConnection and TodoItemQuery. Because of the way @nestjs/graphql and nest work we need to extend the QueryArgsType so that it will know the type to serialize into.

In your resolver you can now create a new completedTodoItems method with the following:

todo-item.resolver.ts
import { Filter, InjectAssemblerQueryService, QueryService } from '@ptc-org/nestjs-query-core';
import { ConnectionType } from '@ptc-org/nestjs-query-graphql';
import { Args, Query, Resolver } from '@nestjs/graphql';
import { TodoItemDTO } from './dto/todo-item.dto';
import { TodoItemAssembler } from './todo-item.assembler';
import { TodoItemConnection, TodoItemQuery } from './types';

@Resolver(() => TodoItemDTO)
export class TodoItemResolver {
  constructor(@InjectQueryService(TodoItemEntity) readonly service: QueryService<TodoItemEntity>) {}

  // Set the return type to the TodoItemConnection
  @Query(() => TodoItemConnection)
  completedTodoItems(@Args() query: TodoItemQuery): Promise<ConnectionType<TodoItemDTO>> {
    // add the completed filter the user provided filter
    const filter: Filter<TodoItemDTO> = {
      ...query.filter,
      ...{ completed: { is: true } },
    };

    return TodoItemConnection.createFromPromise((q) => this.service.query(q), { ...query, ...{ filter } });

}


Lets break this down so you know what is going on.

In the above code we annotate the new method with

@Query(() => TodoItemConnection)

The return type passed to query lets graphql know what the generated schema type is.

The next piece to pay attention to is

completedTodoItems(@Args() query: TodoItemQuery)

We use the TodoItemQuery we created for the arguments type and annotate with @Args when you look at the generated schema in it will look like.

completedTodoItems(
  paging: CursorPaging = {}
  filter: TodoItemFilter = {}
  sorting: [TodoItemSort!] = []
): TodoItemConnection!

Notice how there is not a query arg but instead the you see the fields of TodoItemQuery that is because we used @Args without a name and added the @ArgsType decorator to the TodoItemQuery.

The next piece is

// add the completed filter the user provided filter
const filter: Filter<TodoItemDTO> = {
  ...query.filter,
  ...{ completed: { is: true } },
};

Here we do a shallow copy of the filter and add completed: { is: true }. This will override any completed arguments that an end user may have provided to ensure we always query for completed todos.

Finally we call create our connection response by using the createFromPromise method on the connection.

// call the original queryMany method with the new query
return TodoItemConnection.createFromPromise((q) => this.service.query(q), { ...query, ...{ filter } });

The last step is to add the resolver to the module, by registering our resolver as a provider and importing the NestjsQueryGraphQLModule we will get both the auto generated resolver along with the custom endpoints from the custom resolver.

todo-items.module.ts
import { NestjsQueryGraphQLModule } from '@ptc-org/nestjs-query-graphql';
import { NestjsQueryTypeOrmModule } from '@ptc-org/nestjs-query-typeorm';
import { Module } from '@nestjs/common';
import { TodoItemDTO } from './dto/todo-item.dto';
import { TodoItemAssembler } from './todo-item.assembler';
import { TodoItemEntity } from './todo-item.entity';
import { TodoItemResolver } from './todo-item.resolver';

@Module({
  providers: [TodoItemResolver],
  imports: [
    NestjsQueryGraphQLModule.forFeature({
      imports: [NestjsQueryTypeOrmModule.forFeature([TodoItemEntity])],
      assemblers: [TodoItemAssembler],
      resolvers: [
        {
          DTOClass: TodoItemDTO,
          EntityClass: TodoItemEntity,
        },
      ],
    }),
  ],
})
export class TodoItemModule {}