Semantic UI Images

Diff same file between two different commitson the same branch

git diff HEAD~1 HEAD -- app/views/layouts/application.html.erb

This will diff the current commit with the previous commit.

Find all the Replace by Chaining ack output to sed

From the command line, I was able to replace Bootstrap 3 classes with Bootstrap 4 class using

ack, sed and xargs. 

ack "search text" -l --print0 | xargs -0 -n 1 sed -i "s/search text/replacement text/"

Reference:

Sed recursively with the help of ack and xargs
 

Top 3 Lessons from Successful Open Source Projects

1. Every good work of software starts by scratching a developer's personal itch.
2. Good programmers know what to write. Great ones know what to rewrite (and reuse).
3. Smart data structures and dumb code works a lot better than the other way around.

Linux was not written from scratch. Linus Torvalds took the Minix as the starting point. It is easier to start from a good partial solution. Minix provided the scaffold and eventually the Minix code was either rewritten or deleted. Read more at Cathedral Bazaar

Organized Topics for Coding Skills

Big O Notation

Construction of Loops
Establishing Initial Conditions for Loops
Finding the Iterative Construct
Termination of Loops
Iteration Trace Table
Iterative Program Structure
While Loop Structure
For Loop Structure
For Loop Examples
Comparison: Loops vs Recursive Functions

Divide-and-Conquer
Recursion : Algorithmically, Semantically
How to Code Recursively
Stack Overflow Example
Compute a to the power b
Induction and Recursion

Summation Algorithm
Add a sequence of numbers
Recursion
Iteration
Recursive Sum

Multiplication
Iterative Solution
Recursive Solution

Division without divide operator
Trace : Desk Check a solution
Non-Linear Recursion

Factorial
Recursive Solution
Optimized Solution
Factorial Call Stack
Factorial Algorithm
Factorial Implementation

Compute a to the power b
Recursion Solution
Iterative Solution

Compute a % b
Iterative Solution
Efficient Solution

Fibonacci : Multiple Bases Cases - Recursion
Efficient Fibonacci
Fibonacci Runtime
Fibonacci Number Efficiency
Fibonacci Iterative Solution

Dynamic Programming

Square Root Desk Check Table
Binary Recursion
Even Number
Square Root
Linear Recursion

Exponentiation Function
Factorial C
Array C
Binary Search C
Reverse String C
Sum the Digits

Find Repeating Elements
Identical
Unique Characters
Unique Characters with Constraints
Duplicate Elements in Array
Recognize Non-Linear Recursion
Add Adjacent Elements
Runtimes + , *
Powers of 2 from 1 through n
Remove White Spaces
Remove Duplicates in a String
String Segmentation
Palindrome
Palindrome Substrings Diagrams
Palindrome

Images Datatables

How to override merge conflict

To use the latest git version of the file. We can replace file that has conflict with the latest from repo by running these commands:

git reset -- path/to/file.ext

git checkout path/to/file.ext

Find and Replace a Term in All Files in All Directories from a Given Directory

find ./ -type f -exec sed -i -e 's/apple/orange/g' {} \;




Unable to download data from https://rubygems.org/ - SSL_connect returned=1

gem install rails -v 4.1

ruby -ropen-uri -e 'eval open("https://git.io/vQhWq").read'

-e:1:in `eval': uninitialized constant OpenSSL::OPENSSL_LIBRARY_VERSION (NameError)

ruby -v -e 'require "openssl"; p OpenSSL'

ruby 2.1.2p95 (2014-05-08 revision 45877) [x86_64-darwin13.0]

OpenSSL

brew rm openssl
brew cleanup openssl
brew install openssl

Installing tiny_tds in Ubuntu

sudo apt-get install freetds-dev

gem install tiny_tds 

Copy / Paste terminal utility for Ubuntu

1. sudo apt-get update
2. sudo apt-get install xclip

Add an alias to the .bashrc file:

alias pbcopy='xclip -sel clip'

I am using the same command that is used on a Mac as the alias. I also have open alias to open a directory from a terminal:

alias open='xdg-open'

no implicit conversion of nil into String

This can happen when you have not defined the required configuration in secrets.yml. For instance, you are using http basic auth and the credentials are not defined in the config file.

Cloudfront

simplehttpserver npm

npm install simplehttpserver -g

simplehttpserver .

simplehttpserver . -p 8081

Converting .avi file to .mp4

Install ffmpeg:

On Mac 10.10.5:

brew install ffmpeg

Sprockets::FileNotFound: couldn't find file 'fingerprintjs2' with type 'application/javascript'

jquery_ujs Uncaught TypeError: $.ajaxPrefilter is not a function

This happened when I copied the started template from Bootstrap 4.1 version. It gives you the slim version of jQuery by default. Use the regular jQuery. https://code.jquery.com/jquery-3.3.1.min.js

In style.scss, include
@import bootstrap

Copy the bootstrap.js to vendor/assets/javascripts directory. Copy bootstrap.css to vendor/assets/css directory.

NeverBounce API

s3 images

Overcoming Mental Hurdles to Software Development

Facing Too Many Unknowns 

Facing many unknowns and working on a new API can be overwhelming. Even if you have the physical and mental energy to work, you can get stuck. I faced this challenge in a recent project. I decided to tackle this by doing an easy task. I copied the basic Bootstrap 4.1 table with hard-coded data and rendered the view in the web app. I was able to see something real, think through vague requirements and asked the stake holder the right questions. If you have a client who only has a vague idea of what they need, it becomes a challenge to gain understanding with minimum amount of code.

Gaining Momentum

I was able to gain momentum by tackling simple tasks related to that feature. Refined the requirements and the user's flow over a few days to come up with more followup questions to finalize the requirements. Once the requirements became clear, I was not coding based on some phantom requirements and designing the complicated database structure that was not even required. The time spent on solving problems that did not exist was very energy draining. I had already spent time on analyzing the flow that could vary due to three variables. This made the solution very complex due to the amount of variations. The code was becoming a big mess.

Focusing on the Core

I drew simple diagrams with boxes and arrows to show the user's flow for different use cases. Discussion with the stakeholder had a structure because we focused only on one use case at a time.  There was no discussion of technology during this conversation. Only golden path scenario was discussed to clarify the requirements. We can add the alternate scenarios later. We can ask questions based on the existing diagrams, reason about what should happen and draw the alternate scenarios separately.

Gaining Business Context

I made the mistake of copying the similar features of other existing products. I realized it was a mistake later because the business context was different. During the conversation based on simple diagrams I was able to understand the business context. I had narrowed the scope of the problem to be solved.  I also pushed back on some requirements and asked the stakeholder to justify why it should be included in version 1. Some of the things might happen once every 3 months does not justify automation and was removed from the stated requirements.

Building a Prototype First

I did not build a prototype because it was a lot easy to use Bootstrap 4.1 with Rails to build the screens with hard coded data. I saved the time to learn a prototyping tool. I was able to focus on learning new AWS APIs that was required to build the product.

Being Agile and Lean

The client was remote and was able to chat via What's app and email few times a week. The requirements were in the emails and were not well thought out to write the test first. Clarify First, Test Later. I did not automate the infrastructure management because at this point I am not sure if I can get 99 clients who will find this product useful without any customization. It has been custom built for this particular client. Reading the lean startup articles, I was confident that I was targeting the right segment in the adoption curve.

Lessons Learned

• Do not write production level code before understanding the business. 
• Draw simple diagrams with technical details to gain business context first.
• Narrow down the scope of the problem before starting to code.
• It's ok to start the first few versions of the screen with existing products from similar domains.
• Remember, these screens need to refined once the business context knowledge is acquired.
• If the complexity of the solution is getting out of control, go back and see if you can push back on the requirements.

AWS S3 Presigned URL

Generating Presigned URL for AWS S3 Files