Sohel Ahmed Mesaniya | Software Engineer

About


Name	Sohel Ahmed
Surname	Mesaniya
Education	B. Tech. in Information Technology
Birth & Residence	Wankaner (Morbi), GJ, India 🇮🇳
Citizenship	Indian
Timezone	Indian Standard Time (IST), UTC + 5:30 India presently does not observe daylight saving time (DST or summer time).

Contact


Email Address	sam.wankaner@gmail.com
Skype	live:sohel.ahmed.m

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Adding "blog" in URL in Gatsby Theme Minimal Blog by LekoArts

Tue, 15 Sep 2020 00:00:00 GMT

This website (https://sohelahmed.site) is using amazing gatsby-starter-minimal-blog by Lekoart. Thanks LekoArts.

This blog came into notice of LekoArts. New plugin option postsPrefix is added in the version 2.7.2 of @lekoarts/gatsby-theme-minimal-blog package. Thanks again LekoArts. It is recommended to upgrade to that version to avoid manually editing URLs.

By default it comes with blog link without "blog" in URL. Example:

If I create a new blog with slug "my-blog-post" the URL for it will be https://sohelahmed.site/my-blog-post. However I wanted "blog" in the URL https://sohelahmed.site/blog/my-blog-post. So it can be achieved by deleting old posts and creating new with "blog" in the URL in gatsby-node.js

/path/to/project/gatsby-node.js

1const withDefaults = require(`@lekoarts/gatsby-theme-minimal-blog-core/utils/default-options`);
2const postTemplate = require.resolve(
3  `@lekoarts/gatsby-theme-minimal-blog-core/src/templates/post-query.tsx`
4);
5const pageTemplate = require.resolve(
6  `@lekoarts/gatsby-theme-minimal-blog-core/src/templates/page-query.tsx`
7);
8const contactPageTemplate = require.resolve(
9  `./src/@lekoarts/gatsby-theme-minimal-blog-core/templates/contactpage-query.tsx`
10);
11
12exports.onCreatePage = ({ page, actions }, themeOptions) => {
13  const { createPage, deletePage } = actions;
14  const old_page = Object.assign({}, page);
15
16  const { basePath, blogPath, tagsPath, formatString } = withDefaults(
17    themeOptions
18  );
19
20  const compo_path = `${process.cwd()}/node_modules/@lekoarts/gatsby-theme-minimal-blog-core/src/templates/post-query.tsx`;
21  if (page.componentPath === compo_path) {
22    deletePage(old_page);
23  }
24};
25
26exports.createPages = async ({ actions, graphql, reporter }, themeOptions) => {
27  const { createPage } = actions;
28
29  const { basePath, blogPath, tagsPath, formatString } = withDefaults(
30    themeOptions
31  );
32
33  const result = await graphql(`
34    query {
35      allPost(sort: { fields: date, order: DESC }) {
36        nodes {
37          slug
38        }
39      }
40      allPage {
41        nodes {
42          slug
43        }
44      }
45      tags: allPost(sort: { fields: tags___name, order: DESC }) {
46        group(field: tags___name) {
47          fieldValue
48        }
49      }
50    }
51  `);
52
53  if (result.errors) {
54    reporter.panicOnBuild(
55      `There was an error loading your posts or pages`,
56      result.errors
57    );
58    return;
59  }
60
61  const posts = result.data.allPost.nodes;
62
63  posts.forEach((post) => {
64    createPage({
65      path: `/${basePath}/blog/${post.slug}`.replace(/\/\/+/g, `/`),
66      component: postTemplate,
67      context: {
68        slug: post.slug,
69        formatString,
70      },
71    });
72  });
73
74  const pages = result.data.allPage.nodes;
75
76  if (pages.length > 0) {
77    pages.forEach((page) => {
78      createPage({
79        path: `/${basePath}/${page.slug}`.replace(/\/\/+/g, `/`),
80        component:
81          page.slug === "/contact" ? contactPageTemplate : pageTemplate,
82        context: {
83          slug: page.slug,
84        },
85      });
86    });
87  }
88};

Sorting calculated columns in Yii2

Mon, 10 Aug 2020 00:00:00 GMT

Sorting the calculated column in the grid might be challenging. From PHP array to database view which approaches to choose and when, are uncovered.

# Calculated column
# PHP
# Proportionality
# Database View
# Versions and Links

Calculated column

Calculated column or field is the column shown in grid view having value not directly stored in relational database, but rather calculated at runtime in PHP. For example, if there is a column "Total Amount" in the "Orders" grid that show total cost of purchased items by

1price of one item * quantity
2+
3similarly add other items

and the "Total amount" is not directly stored in any column of any table in the database, then total_amount is the calculated column.

"Users" grid showing "First Name" that is directly stored in the first_name field/column in the users table in the database is not a calculated column.

PHP

If there are comparatively less records to show in grid (for example less than 250) and it will remain finite in future and its grid contains calculated column, sorting can be done within PHP avoiding ordering from database side or database view.

It can be achieved by loading all the records in the PHP array and hence stored in memory (RAM) and performing sorting on it.

Yii provides amazing in-built way to pass data stored in array to grid by Array Data Provider

Quoting from the Yii docs, it can be achieved by:

1use yii\data\ArrayDataProvider;
2
3$data = [
4    ['id' => 1, 'name' => 'name 1', ...],
5    ['id' => 2, 'name' => 'name 2', ...],
6    ...
7    ['id' => 100, 'name' => 'name 100', ...],
8];
9
10$provider = new ArrayDataProvider([
11    'allModels' => $data,
12    'pagination' => [
13        'pageSize' => 10,
14    ],
15    'sort' => [
16        'attributes' => ['id', 'name'],
17    ],
18]);
19
20// get the rows in the currently requested page
21$rows = $provider->getModels();

This way can be used for config table which contain key-value and have comparatively less number of records and if the config grid has calculated column.

Proportionality

Sorting a particular calculated column can easily be done if its value is directly proportional to other column stored in the database avoiding PHP array and database view. For example, consider a table containing several radiuses of different balls such as table-tennis, cricket, football etc.

id	name	radius
1	Table tennis	2
2	Cricket	4
3	Football	10

Once the radius is known it's volume can be calculated by formula 4/3 π r r r.

Here the radius is directly proportional to volume of ball. If the radius increases the volume increases, and if the radius decreases the volume decreases.

id	name	radius	volume
1	Table tennis	2	33.51
2	Cricket	4	268.08
3	Football	10	4188.79

So a calculated column "volume" in the above grid is added which shows the volume of the ball. And to add the ability to sort on volume column, radius can be used.

1$dataProvider->sort->attributes['volume'] = [
2    'asc' => ['radius' => SORT_ASC],
3    'desc' => ['radius' => SORT_DESC],
4];

Database View

For complex calculated columns, database view can be used. View is a kind of virtual table. Result set of any SELECT query can be made to its own table. Consider example:

Order

id	user_id	created_at
1	1	2010-12-12 00:00:00
2	2	2010-12-13 00:00:00
3	3	2010-12-14 00:00:00

Order Items

id	order_id	product_id	quantity
1	1	1	1
2	2	1	1
3	2	2	1
4	2	3	2
5	3	3	1
6	3	1	1

An order can contain one or more products and each product can have one or more quantities.

Products

id	name	price
1	mobile	10000
2	keyboard	600
3	mouse	200

So orders with their total amount will be:

order_id	total_amount	items
1	10000	1 mobile (10000)
2	11000	1 mobile (10000) + 1 keyboard (600) + 2 mouse (2*200))
3	10200	1 mobile (10000) + 1 mouse (200)

Now sorting on total_amount is needed. First the target is to only create SQL query which give total_amout

The SQL query is:

1select
2    ord.id,
3    ord.user_id ,
4    (
5    select
6        sum(oi_in.quantity * prd_in.price)
7    from
8        orders ord_in
9    left join order_items oi_in on
10        ord_in.id = oi_in.order_id
11    left join products prd_in on
12        oi_in.product_id = prd_in.id
13    where
14        ord_in.id = ord.id ) total_amount
15from
16    orders ord
17order by
18    total_amount asc

And once writing SELECT query is completed, it's view can be easily generated by CREATE VIEW statement.

1CREATE OR REPLACE VIEW order_with_total_amount AS
2select
3    ord.id,
4    ord.user_id ,
5    (
6    select
7        sum(oi_in.quantity * prd_in.price)
8    from
9        orders ord_in
10    left join order_items oi_in on
11        ord_in.id = oi_in.order_id
12    left join products prd_in on
13        oi_in.product_id = prd_in.id
14    where
15        ord_in.id = ord.id ) total_amount
16from
17    orders ord
18order by
19    total_amount asc

Once the view is made, it's search model can be made and thus sorting calculated column in grid can be accomplished.

Orders with total amount

id	user_id	total_amount
2	2	11000
3	3	10200
1	1	10000

Versions and Links

Yii: 2.0.X

PostgreSQL: 12.3

SQL (Postgres) for above schema and data can be found at Gist at GitHub.com: https://gist.github.com/SOHELAHMED7/1a8429d57f9f264eb40b6cfce87439f6

Redis cache in NestJS

Mon, 20 Jul 2020 00:00:00 GMT

Redis is powerful & fast. That is the reason it is used as key-value data storage and cahce system in many web apps. Its example usage in NestJS app by setting and getting cache key-values is demonstrated.

# Installing Dependencies
# Redis Cache
# Links and Miscellaneous

Installing Dependencies

npm install --save cache-manager Generic Cache Manager API provider
npm install cache-manager-redis-store --save Cache Manager API for Redis storage
npm install --save-dev @types/cache-manager Type dependency for TypeScript

Redis Cache

1import * as redisStore from "cache-manager-redis-store";
2import { CacheModule, Module } from "@nestjs/common";
3import { AppController } from "./app.controller";
4import { AppService } from "./app.service";
5
6@Module({
7  imports: [
8    CacheModule.register({
9      store: redisStore,
10      host: "localhost",
11      port: 6379,
12    }),
13  ],
14  controllers: [AppController],
15  providers: [AppService],
16})
17export class AppModule {}

Controller

app.controller.ts

1import { Controller, Get } from "@nestjs/common";
2import { AppService } from "./app.service";
3
4@Controller()
5export class AppController {
6  constructor(private readonly appService: AppService) {}
7
8  @Get()
9  getHello(): Promise<string> {
10    return this.appService.getHello();
11  }
12}

Service

app.service.ts

1import { Injectable, Inject, CACHE_MANAGER } from "@nestjs/common";
2import { Cache } from "cache-manager";
3
4@Injectable()
5export class AppService {
6  constructor(@Inject(CACHE_MANAGER) private cacheManager: Cache) {}
7
8  async getHello(): Promise<string> {
9    // callback way
10    // this.cacheManager.set('foo', 'bar', {ttl: 100000}, (err) => {
11    //   this.cacheManager.get('foo', (err, result) => {
12    //     console.log(result);
13    //   });
14    // });
15
16    await this.cacheManager.set("foo2", "bar2", { ttl: 100000 });
17    const res = await this.cacheManager.get("foo2");
18    console.log(res); // logs "bar2"
19
20    return "Hello World!";
21  }
22}

By sending HTTP GET request at the endpoint of AppController getHello(), bar2 is logged in CLI

Links and Miscellaneous

Official NestJS Cache docs: https://docs.nestjs.com/techniques/caching
Cache manager: https://github.com/BryanDonovan/node-cache-manager
Cache manager for Redis: https://github.com/dabroek/node-cache-manager-redis-store
I have created a pull request that enhance Redis Cache docs in NestJS docs: https://github.com/nestjs/docs.nestjs.com/pull/1254/files

Contagion movie end explained better

Fri, 27 Mar 2020 00:00:00 GMT

Bulldozer is operated by the company AIMM Alderson and is the employer of Beth Emhoff (portrayed by Gwyneth Paltrow), the very first patient. Globalization and Industrialization

Bulldozer cut trees. Deforestation

The natural habitat bats living on that tree are displaced. Displacement.

Bats moves to new place to live: a pig farm

A pig eats a piece of banana that is half eaten by bat

Chef prepares meal from that pig, slaughtered

Meanwhile chef also meets and hand shakes with Beth Emhoff

Beth Emhoff is the index patient.

Noteworthy: Chef did not contract the disease, possibly immune, but he transferred the disease from infected to non-infected body. Currently many governments thinking of or issued "immunity passport" but it is risky

So Industrialization (AIMM Alderson) leads to Deforestation leads to Displacement of natural habitat (bats) leads to pandemic

Displacement of living being, Butterfly effect and "Survival of fittest" are all correlated

Butterfly effect theory e.g.: a flying of a butterfly in Madagascar can result in massive earthquakes in Norway. If some small thing can result in pandemic, then it can also be said that butterfly effect is produced. https://en.wikipedia.org/wiki/Butterfly_effect

Charles Darwin's evolutionary theory of "Survival of the fittest" 's e.g.: a polar bear (indigenous and natural habitat to Arctic circle) is likely to live and sustain for multiple generations in the cold North pole region. If they are moved to a hot region in Africa, say Sahara, they are more likely to die. https://en.wikipedia.org/wiki/Survival_of_the_fittest

Displacement of any living organism or natural habitat is a very big phenomenon.

If human displace all kangaroos from Australia to Latin America, butterfly effect may produce because it will try to violate "survival of the fittest"

Even displacement of the same species animal for e.g. Asian lion and African lion are swapped, might produce butterfly effect

And even one day travel (Displacement) of a human to a nearby city for work can produce butterfly effect. Imaginary e.g. but it can happen in real world:

A person leaves food near his home for birds before going to the office everyday. One day in order to catch the train early to go for work to a nearby city, he forgot it. Crows coming everyday finds that there is no food so they grab some piece of infected meat from somewhere and come back. Leaving that half eaten piece there, the rat smells and touches it. Rat moves to the kitchen of that person and that person is the index patient.

Few people tend to blame big companies (AIMM Alderson) for pollution and deforestation. But that is baseless.

From hair to shoes, comb, dye, shirt, pant, pant zip, mobile, mobile case, shoes, key etc how are all these are manufactured and distributed. How machines manufacturing these items are created and distributed?

We are all in this together, we have to accept it.

More things are taken from earth than given back

So how to avoid it and maintain balance?

Either we can go to per-electricity era, ride horses, do all things manually, don't use modern appliances and services etc.

We can make earth awesome. https://github.com/philsturgeon/awesome-earth

Originally posted as Twitter thread: https://twitter.com/SohelAhmedM/status/1259809770367680514

Authenticate Laravel app with user data stored in JSON file

Tue, 25 Feb 2020 00:00:00 GMT

Authentication in Laravel app can also be done if all the user data in stored in JSON file and not in MySQL, PostgreSQL etc.

# Real World Use Case
# Versions, Links and References

Real World Use Case

Though it is very unlikely that this way of authentication will be used in any real world app, but this implementation can be used to implement custom auth provider which can use Redis, Lightweight Directory Access Protocol (LDAP) etc.

Still there might be some use cases:

If the users info are stored in separate DB and in case if it goes down, its exported backup file can be used here.
If initially the user info (in some cases) are only stored in excel sheet (or json file like here) and then it is required to authenticate the app on the top of that data, this might be helpful.
Using production data in locally running app: Production database have lot of records, and few of them are exported. That exported data can be used in locally running apps.

Versions, Links and References

Laravel: 5.5 (also much relavant to versions till 8.X)

How to implement:

Official Laravel docs explains it amazingly.

https://laravel.com/docs/5.5/authentication#adding-custom-user-providers

Implementation repository - Data stored in JSON file: https://github.com/SOHELAHMED7/json_file_user_provider