New chapter: use structures

content/books/things-i-learnt/_index.md

@@ -30,6 +30,7 @@ template = "section-contentless.html"
 		* [Beware of Interface Changes](interface-changes)
 		* [It's Better To Let The Application Crash Than Do Nothing](crash-it)
 		* [If You Know How To Handle It, Handle It](handle-it)
-		* [Types Say What You Data Is](data-types)
+		* [Types Say What Your Data Is](data-types)
+		* [If Your Data Has a Schema, Use a Structure](use-structures)
 * Community/Teams
 	* [A Language Is Much More Than A Language](languages-are-more)

content/books/things-i-learnt/data-types/index.md

@@ -37,4 +37,4 @@ performance out.
 Fortunately, new languages are based on ML, which wouldn't allow this kind of
 stuff.
 
-{{ chapters(prev_chapter_link="/books/things-i-learnt/handle-it", prev_chapter_title="If You Know How To Handle It, Handle It", next_chapter_link="/books/things-i-learnt/languages-are-more", next_chapter_title="A Language Is Much More Than A Language") }}
+{{ chapters(prev_chapter_link="/books/things-i-learnt/handle-it", prev_chapter_title="If You Know How To Handle It, Handle It", next_chapter_link="/books/things-i-learnt/use-structures", next_chapter_title="If Your Data Has a Schema, Use a Structure") }}

content/books/things-i-learnt/languages-are-more/index.md

@@ -39,4 +39,4 @@ surface of what the whole of a language encapsulates and if you ignore the
 other elements in it, you may find yourself with a cute language in a
 community that is always fighting and never going forward.
 
-{{ chapters(prev_chapter_link="/books/things-i-learnt/data-types", prev_chapter_title="Types Say What You Data Is") }}
+{{ chapters(prev_chapter_link="/books/things-i-learnt/use-structures", prev_chapter_title="If Your Data Has a Schema, Use a Structure") }}

content/books/things-i-learnt/use-structures/index.md

@@ -0,0 +1,58 @@
++++
+title = "Things I Learnt The Hard Way - If Your Data Has a Schema, Use a Structure"
+date = 2019-06-25
+
+[taxonomies]
+tags = ["en-au", "books", "things i learnt", "data classes", "structs"]
++++
+
+You may be tempted to use a list (or tuple, if your language allows) to keep
+your data if it's simple -- like, say, only 2 fields. Don't.
+
+<!-- more -->
+
+Some languages allow unstructured data to be kept in the format of tuples:
+They act like lists, but you can use to store heterogeneous data (which is a
+cute way of "it stores fields of different types").
+
+This languages also allow you to "destructurize" them, so you can extract
+elements from them without directly accessing them by index.
+
+For example, in Python, you can have a tuple with:
+
+```python
+a_tuple = ('A String', 1, 7.5)
+```
+
+And you can destructure it with
+
+```python
+some_string, an_integer, a_float = a_tuple
+```
+
+See? It's simple! You don't need to create a whole structure if you're just
+passing a string, an integer and a float around.
+
+Except, you do.
+
+Tuples and destructuring should be used only when you need to pass data from
+one function to another -- and barely that. When you have this tuple being
+passed around, being destructured and created again -- say, you are adding one
+value of the tuple to another value and producing a new tuple in the same
+format -- then you have a structured data.
+
+And when you have a structured data, you must use a data class or a struct (or
+even
+[NamedTuples](https://docs.python.org/3/library/collections.html?highlight=namedtuple#collections.namedtuple),
+if you're using Python).
+
+Although it may look way more simpler to keep destructuring and building the
+tuple over and over, in the long run you'll end up with a mess 'cause a simple
+change -- like adding a new field -- will require checking every destructuring
+and every creation of the tuple to make sure if will stay in the same shape
+every time.
+
+So: You data has a schema? Use a Data Class or Class or Struct. Only if it is
+schemaless, then you can use a tuple.
+
+{{ chapters(prev_chapter_link="/books/things-i-learnt/data-types", prev_chapter_title="Types Say What Your Data Is", next_chapter_link="/books/things-i-learnt/languages-are-more", next_chapter_title="A Language Is Much More Than A Language") }}