If we would have kept the call to super out of the #initialize_dup method, we would never have called initialize_copy, so it is important to keep that in.

Object hierarchies are very different from relational hierarchies. Relational hierarchies focus on data and its relationships, whereas objects manage not only data, but also their identity and the behavior centered around that data.

(Always call super to inherit the default behavior.)

Adding Object Oriented Principles (OOP) to a functional codebase adds yet another way of writing code, reducing consistency and clarity.

For instance, those who prefer classical inheritance may enjoy the addition of the class keyword, while others may reject it as conflicting with the idea of a prototypical inheritance model.

Internally, it creates and returns a fresh, subclassed activity (via patching) whilst replacing the step for given :id. Be advised that this does not change the original activity class.

It reminds us that rather than asking an object for data and acting on that data, we should instead tell an object what to do.

The central ideas of this design pattern closely mirror the semantics of first-class functions and higher-order functions in functional programming languages. Specifically, the invoker object is a higher-order function of which the command object is a first-class argument.

In object-oriented programming, information hiding (by way of nesting of types) reduces software development risk by shifting the code's dependency on an uncertain implementation (design decision) onto a well-defined interface. Clients of the interface perform operations purely through it so if the implementation changes, the clients do not have to change.

Though getter/setter methods are commonplace in Java, they are not particularly object oriented (OO). In fact, they can damage your code's maintainability. Moreover, the presence of numerous getter and setter methods is a red flag that the program isn't necessarily well designed from an OO perspective.

The changes we needed to make to main to reassign post mean that this implementation doesn’t quite follow the object-oriented state pattern anymore: the transformations between the states are no longer encapsulated entirely within the Post implementation. However, our gain is that invalid states are now impossible because of the type system and the type checking that happens at compile time! This ensures that certain bugs, such as display of the content of an unpublished post, will be discovered before they make it to production.

"Objects in a program should be replaceable with instances of their subtypes without altering the correctness of that program." See also design by contract.

some programming languages that provide lexical closures view encapsulation as a feature of the language orthogonal to object orientation.

A paradigm is a model or pattern. In JavaScript, there are a number of popular paradigms including object-oriented programming (OOP) and functional programming (FP). Paradigms are more important than is sometimes recognized. They help form mental models for solving problems. Becoming well-versed in the principles of a given paradigm can help accelerate development by providing mental shortcuts for solving the challenges that arise while building applications. They can also help produce higher quality software.

for example, comments and identifiers

If one object is part of another object, then we use a diamond at the start of the arrow (next to the containing object), and a normal arrow at the end.

Grid devices can be nested or layered along with other devices and your plug-ins,

a mutator method is a method used to control changes to a variable. They are also widely known as setter methods

class MyClassDef {

    public void setProperty(String propertyVal) { .. }

}