What I’ll do this week (February 26)

There are a lot of things that I’d like to do, I’ll enumerate them in order of importance.

  • Search pools and users, that implies that I need to create a way to query a regular expresion or at least the begining of one of their string properties. I also need to filter the pools by its `public` property.
  • Pool owners need to split the bill, they should be given the options of spliting it evenly or with custom amounts (do we need to make sure that the total of all the custom amounts sum up to the total of the bill?).
  • Pool needs to specify who you should pay to, how much money do they owe or who payed more than necessary.
  • The only payment method available right now is cash, the pool owner should be the only one able to change the pool and relation to the pool properties.
  • Maybe invites should be visible through an interface in the app, I think that the best way to approach this is to create a new relation between the pool node and user node that indicates that he’s been invited. Because otherwise there is no other way to find out who you have invited, the email is send and after that it all depends on the user clicking the link.
  • We need a Facebook and Google login (I think this will be done by someone else).
  • User profile images are not critical (because we have default profile gravatars) but would be nice to have, we should store them somewhere outside the database, maybe store the path to the file in the node, or use an external service like Amazon S3.

What I did this week (February 19)

This week I advanced a lot in the relation api for neo4j, altough I’d like to improve it, we can get along with it for whole project. Also, in the Cooper api, we can now create, join pools, users can invite other users and invitation links are sent to them via email. Marco and Poncho managed to have a beta version of the Android app, most of the api functionality is already implemented in the app. It’s been a productive week.

Code reusability: don’t reinvent the wheel

As the title says, it is completely unnecessary to rewrite code that it has already been written, it is, most of the time, a waste of your time and effort. With all the open source code available nowadays, it is really probable that you find whatever you are looking for on sites like github, gitlab, bitbucket or any other site, and if you don’t find it, well, then now you know what’s going to be your next open source contribution. You should really focus on writing building on top of what others have already done, also, it is worth to notice that you should be writing reusable code as well.

Some tips on writing reusable code:

  1. Don’t repeat yourself: if you find yourself writing the same code several times, probably you should move that piece of god to a module or something alike.
  2. Make a class/method do just one thing: remember the Unix philosophy? write programs that do one thing and do it well, also, write these programs to work together, the secret is in writing generic code to accomplish one simple thing, then use the output of that as input of another program to accomplish a more complex task, don’t make code too generic tough, or it will be difficult to find a purpose to it.
  3. Write unit tests for your classes and make it easy to test classes.
  4. Remove the business logic or main code away from any framework code.
  5. Try yo think more abstractly and use Interfaces and Abstract classes.
  6. Write code that can be easily extended in the future, for code leverage of course.
  7. Don’t write code that isn’t needed, if you doubt if the code is needed, then it is not, just leave it out.
  8. Try to reduce coupling, avoid modules/classes depending on each other.
  9. Be more modular, again, the Unix philosophy.
  10. Write code like your code is an External API, write everything modular and do one thing, then make these components work together to accomplish one common objective, by the end of the day you will have nice, modular and reusable code.




What’s the use of code reuse?



Software Verification and Validation

Validation and verification are two different concepts in software engineering, each one can be abbreviated to the questions: are we building the right system? and are we building the system right?


Validation is concerned with checking that the software actually satisfies the customer’s needs and its objective is to demostrate that the product fulfills its intended use when placed in its intended enviroment, whereas verification is the process which checks if the software is functioning correctly and its objective is to ensure that work products meet their specified requirements.


The difference between Verification and Validation

Verification vs Validation


User Interface Design

User Interface Design focuses on anticipating what users might need to do and ensuring that the interface has elements that are easy to access, understand and use to facilitate those actions.

The reaction or the experience of the user when ising software doesn’t only depend on the functionality and the aesthetically design, what more influences the user to feel comfortable or not is the user interface.


Gestalt Design Principles

Similarity: occurs when objects look similar to one another.

Continuation: occurs when the eye is compelled to move through one object and continue to another object.

Closure: occurs when an object is incomplete or a space is not completely enclosed.

Proximity: occurs when elements are placed close together.

Figure and Ground: The eye differentiates an object from its surrounding area. a form, silhouette or shape is naturally perceived as figure, while the surrounding area is perceived as ground.


flickr photo by Isaac Kohane https://www.flickr.com/photos/52786697@N00/15857500937 shared under a Creative Commons (BY-SA) license

Best practices for User Interface Design

  • Keep the interface simple
  • Create consistency and use common UI elements
  • Be puposeful in page layout
  • Strategically use color and texture
  • Use typography to create hierarchy and clarity
  • Make sure the system communucates what’s happening
  • Think about the defaults





Software Maintenance

Software maintenance stands for all the modifications done after the delivery of a software product. A software maintenance is needed in order to mantain our software up to date.

Modifications in the software may be required because of changes in the market conditions, changes in the client requirements or even host modifications.

There are some types of maintenances based on their characteristics:


flickr photo by Pia https://www.flickr.com/photos/omgdolls/16382202136 shared under a Creative Commons (BY-SA) license

Corrective Maintenance:

This includes modifications and updates done in order to correct or fix problems, which are either discovered by user or concluded by user error reports.

Adaptative Maintenance:

This includes modifications applied to keep the software product up-to date and tuned to the ever changing world of technology and business environment.

Perfective Maintenance:

This includes updates done in order to keep the software usable over long period of time. It includes new features, new user requirements for refining the software and improve its reliability and performance.

Preventive Maintenance:

It aims to attend problems, which are not significant at this moment but may cause serious issues in future.





Open Source Software

Open Source Software (OSS) is software which source code and other rights, that normally belong exclusively to those who have author rights, are published under a software license compatible with the Open Source Definition or are part of public domain.

Now users are able to use the software for free, change, improve and redistribute the software.

There are several Open Source licenses, such as GNU General Public License (GPL), MIT,  Apache License 2.0, Mozilla Public License 2.0 etc.

Mapa conceptual del software libre

Mapa conceptual del software libre – René Mérou – http://es.gnu.org/~reneme/map/es/ – CC BY-SA 3.0

Here’s how to fix a linux computer

By the Oatmeal, have fun.


How to fix a Linux Computer – The Oatmeal