Home A - Z
Page Index

An Otter Wiki

Blame

3aab9f lisa 2026-08-11 23:24:06
Add C06 skill-code study pages, linked from the SD hub Eleven pages ported from the applied-computing-au C06-Reference-Godot standard: home page with the 34-code lookup, per-topic pages with labelled GDScript examples, evidence standards, and Check Your Understanding fold blocks. Generated mirror — repo copy is canonical. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
1 
<!-- Generated from applied-computing-au vic/unit3-4/sat/C06-2026/C06-Reference-Godot — do not hand-edit; re-run the port. -->
2
# Data Structures — GDScript
3
4
5
**Skill codes on this page**
6
7
| Code | Level | Skill |
8
|---|---|---|
9
| C635 | 5–6 | arrays |
10
| C636 | 5–6 | records |
11
| C638 | 5–6 | identifies, in the internal documentation, why the selected data types and data structures were used |
12
13
**Definition.** A *data structure* is a method of organising data to allow particular operations to be performed on it efficiently.
14
15
## C635 — Arrays
16
17
**Definition.** A list of elements indexed by position. In most programming languages, the first element has index zero.
18
19
```gdscript
20
# C635 — Array[float]: fares need decimal places
21
var fares: Array[float] = [5.30, 8.00, 11.20]
22
23
func show_fare() -> void:
24
$ResultLabel.text = "Zone 1: $" + str(fares[0])
25
```
26
27
Typed (`Array[float]`) earns it. Bare `var fares = []` does not — no type for the marker to see.
28
29
**In tile-matching-game** (`board.gd`) — a typed array of your own class:
30
31
```gdscript
32
# tile-matching-game — board.gd
33
var found: Array[Card] = [] # C635 — Array[Card]: only cards can get in
34
for child in get_children():
35
if child is Card:
36
found.append(child)
37
```
38
39
**Two-dimensional array** — a grid organised into rows and columns, accessed with two indices:
40
41
```gdscript
42
# C635 — 2D array: fare by [zone][day type], 0 = weekday, 1 = weekend
43
var fare_grid: Array = [
44
[5.30, 3.60],
45
[8.00, 5.40],
46
]
47
48
var weekend_zone2: float = fare_grid[1][1]
49
```
50
51
## C636 — Records
52
53
**Definitions.**
54
55
- *Record:* a complete set of fields relating to an entity, such as a person.
56
57
- *Field:* a single data item in a record (e.g. `FamilyName`).
58
59
GDScript has no `record` keyword — a **Dictionary** is the everyday record, one key per field:
60
61
```gdscript
62
# C636 — record: one journey, fields of different types
63
var journey: Dictionary = {
64
"date": "2026-08-11",
65
"zone": 2,
66
"fare": 8.00,
67
"concession": false,
68
}
69
70
print(journey["fare"]) # access one field
71
```
72
73
**In tile-matching-game** (`deck.gd`) — each CSV row becomes a record, and the deck is an array of them:
74
75
```gdscript
76
# tile-matching-game — deck.gd
77
cards.append({
78
"pair": pair, # C636 — fields: which card matches which
79
"text": row[1].strip_edges(),
80
"image": row[2].strip_edges() if row.size() > 2 else "",
81
})
82
```
83
84
An **array of records** is a table — the shape most SAT data layers need:
85
86
```gdscript
87
# C635 + C636 — a table: array of journey records
88
var journeys: Array[Dictionary] = []
89
90
func add_journey(zone: int, fare: float) -> void:
91
journeys.append({"zone": zone, "fare": fare})
92
```
93
94
A **custom class** is the stronger record — typed fields the editor can check — and doubles as level 9–10 evidence (see [OOP Concepts](/sd/C06/OOP%20Concepts)).
95
96
**In club-ladder** (`team.gd`) — the class-as-record, real: its own doc comment says "A Team is plain data."
97
98
```gdscript
99
# club-ladder — team.gd
100
class_name Team
101
extends RefCounted
102
103
var team_name := "" # C636 — the fields of the record
104
var wins := 0
105
var draws := 0
106
var losses := 0
107
```
108
109
An `Array[Team]` (`season.gd`) is then the table — the class version of the array-of-dictionaries above.
110
111
## C638 — Why these types and structures
112
113
Level 5–6 asks you to **identify** the reason in internal documentation — one line on each structure:
114
115
```gdscript
116
# C638 — Array[Dictionary]: journeys arrive one at a time in order (array),
117
# and each journey has mixed-type fields (record)
118
var journeys: Array[Dictionary] = []
119
```
120
121
The "why" comes from how the structure behaves — see the input/storage/output table in [Data Type Characteristics](/sd/C06/Data%20Type%20Characteristics).
122
123
**Model documentation in the wild:** the header comment of `tile-matching-game/deck.gd` identifies the whole design — one CSV row per card face, rows sharing a `pair` value match — before any code runs. That is C638 done as a file-level comment.
124
125
## Check Your Understanding
126
127
1. Why does `var scores = []` fail C635?
128
129
>| ### Answer
130
>| It is untyped — `Array[int]` (or a comment naming the type) is required, so the marker can assess the choice.
131
132
2. Name two ways to build a record in GDScript.
133
134
>| ### Answer
135
>| A Dictionary with one key per field, or a custom class with typed fields (the stronger version).
136
137
3. What everyday shape is an "array of records"?
138
139
>| ### Answer
140
>| A table — one record per row, like journeys or teams.