Substitutability is a principle in object-oriented programming stating that, in a computer program, if S is a subtype of T, then objects of type T may be replaced with objects of type S (i.e. an object of type T may be substituted with any object of a subtype S) without altering any of the desirable properties of the program (correctness, task performed, etc.). More formally, the Liskov substitution principle (LSP) is a particular definition of a subtyping relation, called (strongbehavioral subtyping, that was initially introduced by Barbara Liskov in a 1987.

The Liskov Substitution Principle is the third of Robert C. Martin’s SOLID design principles. It extends the Open/Closed principle and enables you to replace objects of a parent class with objects of a subclass without breaking the application. This requires all subclasses to behave in the same way as the parent class.


Functions that use pointers or references to base classes must be able to use objects of derived classes without knowing it.” – Robert C. Martin

A violation of this behaviour would imply your code is not SOLID and it may be prone to malfunctioning.

Google play app review times


The fast boy is no longer the quickest.

Google used to publish Apps almost instantly, no quality review whatsoever, as result, the Google Play Store was full of garbage. Crappy Apps, malicious Apps and overall useless Apps were rampant. Several scandals and privacy breaches after, Google said, no more… “We will review the Apps and ensure some quality across the board”, (turns out that, although criticized, Apple was right, all the time).

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A brand new way to understand your code.

This classy guy can help you understand the code better!

I think that one of the most intimidating experiences, when you try to contribute to an existing codebase, is to obtain an overview of the project. How many times have you felt the urge to help with an open-source project in GitHub but immediately felt like it was an overwhelming task? I might have stumbled upon a possible solution or at least a way to ease your journey when facing this issue.

Since I finished the first version of GoPlantUml, I have received excellent feedback from users and contributors. However, the most interesting one was from users that generated the diagrams but did not understand how to see it. GoPlantUML is a library by design. Although it works as a command, its purpose is to generate plantuml diagrams from your local code. But the key is that is is a library and not a command. So it occurred to a friend of mine and me that we could build a service using this library to generate diagrams from public repositories. And consequently, was born.

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Listening to EXOplayer events

Kotlin 2020 solution approach UPDATE

Events such as changes in state and playback errors are reported to registered Player.EventListener instances.

Player.EventListener has empty default methods, so you only need to implement the methods you’re interested in.

First your class, say your activity, has te conform to the Player.EventListener interface.

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Change created by commented code tag in XcodE

Change created by tag in Xcode… Simple TIP!

If you want to change the header commented code tag

//  Created by {my name here} on 8/4/20.
//  Copyright 2020 __{my company name here}__. All rights reserved.

This name and company template is usually filled with your User and Company, the one is set on: System Preferences –> Users & Groups –> Current User

But if you have a different User, like a private or trivial one, regardless, you can change this name and other variables in the file header by creating a property list file called: IDETemplateMacros.plist

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kotlinx.serialization library, the chosen one

It seems clear today that kotlinx.serialization is the chosen one.

Among all the many libraries to parse JSON with Kotlin in Android. Say… Klaxon, Jackson, Gson, Json2kotlin, etc. kotlinx.serialization is presently attested champion.

There’s no doubt kotlinx.serialization is the future as it is part of Kotlin libraries now. Although it is still at the time of writing this post in incubator stage.

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An easy way to generate your color palette for Android and iOS is a free, no trick, easy grab, palette tool that will allow you compose your color harmony for Android and iOS in a very simplistic way.

This website is based on Material Design, which is a design language developed by Google. Very popular across the board. here you may find a large array of colors and easily generate primaryColor, primaryLightColor, primaryDarkColor, secondaryColor, primaryTextColor, etc.

On top of that, it will allow you to download straightaway a colors.xml or colors.xml file with all the constants well defined, which is pretty convenient. Ready to drop into your Android Studio or XCode project.

Fancy trying? Take a look at it!