Revert back to previous Django Migration

This procedure is only for the development environment while actively working on changes. Say you have several migrations already created but since after making changes realized that some of them are unnecessary and you want to come up with just one migration before checking in code for production deploy. This procedure will revert back migrations to previous level and then will give opportunity to create just one migration file that can then be deployed to production. This can potentially damage databases if not applied properly so use your discernment.

1. Show migrations for an app
$ python3 manage.py showmigrations orchestrator
...
 [X] 0051_auto_20191217_2328
 [X] 0052_auto_20200212_2250
 [X] 0053_job_miscellaneous

2. If you want to revert back the last 2 migrations
$ python3 manage.py migrate orchestrator 0051_auto_20191217_2328
Operations to perform:
  Target specific migration: 0051_auto_20191217_2328, from orchestrator
Running migrations:
  Rendering model states... DONE
  Unapplying orchestrator.0053_job_miscellaneous... OK
  Unapplying orchestrator.0052_auto_20200212_2250... OK

3. Show migrations again
$ python3 manage.py showmigrations orchestrator
...
 [X] 0051_auto_20191217_2328
 [ ] 0052_auto_20200212_2250
 [ ] 0053_job_miscellaneous

4. Delete the undesired migration files
$ rm 0052_auto_20200212_2250.py 0053_job_miscellaneous.py

5. Show migrations again
$ python3 manage.py showmigrations orchestrator
...
 [X] 0051_auto_20191217_2328

6. Now make a new migration. This will have all latest changes in model
$ python3 manage.py makemigrations
Migrations for 'orchestrator':
  orchestrator/migrations/0052_job_miscellaneous.py
    - Add field miscellaneous to job

7. Now apply new migration
$ python3 manage.py migrate
Running migrations:
  Applying orchestrator.0052_job_miscellaneous... OK

Use CSS flexbox for elements to wrap automatically while centered

I learned from this post:

.flex-container-center {
  padding: 0 20px 0 20px;
  display: inline-flex;
  flex-wrap: wrap;
  justify-content: center;
  width: 100%;
}

Getting Started with Angular NgRx

1. Install ngrx
$ yarn add @ngrx/store

2.  Install Redux Store dev tools
Install chrome browser Redux DevTools extension
$ yarn add @ngrx/store-devtools

3. Install NgRx Effects
$ yarn add @ngrx/effects

Typescript (Javascript) Cheat Sheet

1. Falsy values
false — boolean false
0 — number zero
“” — empty string
null
undefined
NaN — Not A Number

2. Immutability conversion
mutable:
this.currentUser.classes.push(classId);

immutable:
this.currentUser = Object.assign({}, this.currentUser,
     {classes: this.currentUser.classes.concat([classId])});

mutable:
user.classes = user.classes || [];
this.currentUser = user;

immutable:
this.currentUser = Object.assign({}, user,
     {classes: user.classes || []});

Bash script for switching branches in Git

This script follows my workflow of switching between different branches in my dev environment:
1. Stash changes in my current branch.
2. Checkout the other branch.
3. Apply previously saved stash on the switched branch.

#!/bin/bash

echo "Switching to $1 branch..."
BRANCH=$(git branch | grep \* | cut -d ' ' -f2)
STASHNAME="$BRANCH-changes"
git stash save "$STASHNAME"
git checkout $1
LATEST=$(git stash list | grep $1 | head -n 1)
echo "Latest stash: $LATEST"
echo "Do you want to apply this stash? [y/n]: "
read apply_stash
if [ "$apply_stash" == "y" ]; then
    STASHED=$(git stash list | grep $1 | head -n 1 | cut -d ":" -f1)
    git stash apply "$STASHED"
fi

Getting Started with NativeScript

Setup development environment using this post.
1. Install node.
2. Install NativeScript CLI
$ npm install -g nativescript
3. Test install
$ tns
4. Install iOS and Android requirements
$ ruby -e "$(curl -fsSL https://www.nativescript.org/setup/mac)"
5. Source bash profile
$ source ~/.bash_profile
6. Verify
$ tns doctor
No issues were detected.

Create first app
1. Create Android Virtual Device(AVD)
$ sdkmanager "system-images;android-25;google_apis;x86"
$ avdmanager create avd -n test -k "system-images;android-25;google_apis;x86"
2. Create app
$ tns create HelloWorld --template tns-template-blank-ng
3. Run the app
$ cd HelloWorld
$ tns run android

Python Packaging

Following this quickstart, this and this.

1. Pick a name and make sure it is unique after checking on pypi, you might want to make this public later on.

2. Create the scaffolding.
maestroclient
├── LICENSE.txt
├── README.txt
├── maestroclient
│   └── __init__.py
└── setup.py

3. Edit setup.py to contain...
from setuptools import setup

setup(name='maestroclient',
      version='0.1',
      description='Client for accessing Maestro API',
      author='Sam Dela Cruz',
      author_email='s@gmail.com',
      license='MIT',
      packages=['maestroclient'],
      install_requires=[
          'requests',
          'urllib3',
      ],
      zip_safe=False)

4. Create a distribution.
$ python3 setup.py sdist

5. Publish on pypi, just so the project name can be reserved to pypi.
$ twine upload dist/*

6. After building the package, if publishing to pypi is not desired, the package can also be hosted anywhere and can be installed using pip as follows...
$ pip3 install http://whatever.web/maestroclient-0.1.tar.gz