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 (strong) behavioral 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.
material.io 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.
https://material.io/resources/color 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.
It’s sometime confusing for new developers
(or rather new Watch iOS developers) to find exactly where to set the Watch
Icons. Well… it’s actually pretty simple.
It may be a bit unclear, because if you use a standard XCode template App, you may find two Assets.xcassets. The first would be under the WatchKit App and the second one under the Watch Kit Extension, usually where you insert your code logic.
Submissions for mobile apps for iOS are subject to approval by Apple’s App Review team, as outlined in the SDK agreement, for basic reliability testing and other analysis, before being published on the App Store.
Applications may still be distributed ad hoc if they are rejected, by the author manually submitting a request to Apple to license the application to individual iPhones, although Apple may withdraw the ability for authors to do this at a later date.