Application - Server - Supscription & Upload file

Administrator 9/18/2021 NestJsGraphQL

# Supscription:

Tạo kết nối realtime giữa client và server. Đầu tiên cần Enable giá trị installSubscriptionHandlers: true trong GraphQlService và subscriptions để verify token.

VD tạo subscription gửi thông báo cho client.

GraqhQL Schema:

type NotifySubscription {
    userId: String
    message: String
    createdAt: String
}

type Subscription {
    notify: NotifySubscription! @isAuthenticated
}

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Resolver:

import { PubSub } from 'graphql-subscriptions';

const pubSub = new PubSub();

...

@Subscription('notify')
notify() {
    return pubSub.asyncIterator('notify');
}

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Dùng class PubSub để kết nối App code (Nesjs) và GraphQL subscriptions engine. Subscribe qua method asyncIterator với tham số trigger name "notify".

Publish:

Publish data bằng method publish

const notify = {
    userId: user._id, 
    message: "Welcome to app!", 
    createdAt: new Date()
};
pubSub.publish('notify', {notify});

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# Upload file:

Scalars: Mặc định GraphQL có các type: Int, Float, String, Boolean and ID. Tạo thêm type Upload cho mutation upload file.

@Scalar('Upload')
export class Upload {
  description = 'Upload custom scalar type';

  parseValue(value) {
    return GraphQLUpload.parseValue(value);
  }

  serialize(value: any) {
    return GraphQLUpload.serialize(value);
  }

  parseLiteral(valueNode, variables) {
    return GraphQLUpload.parseLiteral(valueNode, variables);
  }
}

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Khai báo provider tại module:
```
providers: [
    Upload,
],
```
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GraqhQL Schema:

type Mutation {
    profileAvatarUpdate(file: Upload!): Boolean @isAuthenticated
}

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Resolver:

import { GraphQLUpload, FileUpload } from 'graphql-upload';
import { createWriteStream } from 'fs';

@Mutation(() => Boolean)
async profileAvatarUpdate(
    @Context('currentUser') currentUser: User,
    @Args({name: 'file', type: () => GraphQLUpload}) fileUpload: FileUpload,
    ): Promise<boolean> {

        const {createReadStream, filename} = fileInput;
        return new Promise(async (resolve, reject) =>
          createReadStream()
            .pipe(createWriteStream(`/upload/${filename})`)
            .on('finish', () => resolve(true))
            .on('error', (err) => {
              logger.error(err.toString());
              reject(false);
            }),
        );

}

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Series:

GitHub: https://github.com/ninhnguyen22/nestjs-angular-graphql (opens new window)

NiN

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