Trying to write a bit about OOP

content/thoughts/the-types-of-oop.md

@@ -0,0 +1,105 @@
++++
+title = "The Types of OOP"
+date = 2022-05-31
+draft = true
+
+[taxonomies]
+tags = ["programming", "oo"]
++++
+
+I'm seeing that a large group of newcomers don't get the idea behind object
+oriented programming. And I think this misunderstanding is basically the way
+this is explained.
+
+<!-- more -->
+
+If we take a page from the classical "first look" at OOP, we would see something
+like
+
+```python
+class Animal:
+	def say(self):
+		print("Don't know what to say")
+
+class Dog(Animal):
+	def say(self):
+		print("Woof!")
+```
+
+The example usually creates a base class, with a method (function), extends the
+base class in a child class and overrides the method. And that's basically it.
+
+But, in real life, things are not quite like that.
+
+Ok ok, there are examples in real life that are basically that, but I don't
+think we *start* with that, we *use* that.
+
+So, what do I mean by "Types of OOP"?
+
+## The Grouping
+
+One of the types of OOP we usually do is "grouping". What do I mean by that is
+that we usually have a group of values that are related and should be worked
+together.
+
+For example, in stock markets, we have the concept of a "candle": The candle
+summazes what happened in a period of time -- be it one day, one hour, one
+minute of 10 milliseconds. In that space of time, we capture the first value
+seen, the last value, the highest value and the lowest value. We could, for
+example, use a series of arrays for that, like
+
+```python
+first_values = [10, 20, 14, 21, 17]
+last_values  = [20, 14, 21, 17, 12]
+high_values  = [30, 20, 21, 21, 18]
+low_values   = [9 , 14, 13, 17, 12]
+```
+
+Here, each "column" represents one entry in the period time; if we are doing it
+per hour, that means in the first collected hour we have the values in the first
+column, one hour later we have the values in the second column and so on. Thing
+is, those values are related, and we could basically group them together.
+
+```python
+class Candle:
+	def __init__(self, first, last, high, low):
+		self.first = first
+		self.last = last
+		self.high = high
+		self.low = low
+
+entries = [
+	Candle(10, 20, 30, 9),
+	Candle(20, 14, 20, 14),
+	Candle(14, 21, 21, 13),
+	Candle(21, 17, 21, 17),
+	Candle(17, 12, 18, 21),
+]
+```
+
+This is basically the same thing, but now instead of having multiple arrays, we
+have just one that keeps all related information together. The concept of
+grouping information like that is not something new and even C had a `struct` to
+keep related values together. But when we use objects, we can also add
+"behaviours" to our data, and we could ask if the candle is going up or down, if
+that would help us in our requirements.
+
+A simple example could be the name of a person
+
+```
+class Name:
+	def __init__(self, first_name, last_name):
+		self.first_name = first_name
+		self.last_name = last_name
+
+	def full_name(self):
+		return "{} {}".format(self.first_name, self.last_name)
+```
+
+For a person, we have related information like the first name and last name. But
+if we want to put their names in an envelope, we need to print both names
+together, so we added a "behaviour" (method) to produce that for us.
+
+Quite simple.
+
+## The Façade