Home A - Z
Page Index

An Otter Wiki

Blame

36b863 lisa 2026-08-12 09:10:36
Add C07 study pages; regenerate C06 via the shared port script sd/C07: home + Naming Conventions, Internal Documentation, Validation Techniques (21 skill codes), linked from the SD hub. sd/C06 pages regenerated by sat/port-reference-godot-to-wiki.py (marker update; C06-home now generated from the repo README like every other page). Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
1 
<!-- Generated from applied-computing-au vic/unit3-4/sat/C06-2026/C06-Reference-Godot by port-reference-godot-to-wiki.py — do not hand-edit; re-run the port. -->
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>
2
# Local and Global Variables — GDScript
3
4
5
**Skill codes on this page**
6
7
| Code | Level | Skill |
8
|---|---|---|
9
| C621 | 3–4 | local variables |
10
| C622 | 3–4 | constants |
11
| C628 | 3–4 | uses data types for local variables |
12
| C631 | 5–6 | global variables |
13
| C634 | 5–6 | uses appropriate data types for global variables |
14
15
**Definition.** A *variable* stores and labels data to be referenced and manipulated in a program. Its **scope** is the part of the program that can see it.
16
17
| | Where it is written | Who can see it |
18
|---|---|---|
19
| **Local (C621)** | Inside a function | Only that function |
20
| **Global (C631)** | Outside every function, at script level | Every function in the script |
21
22
**Quick check:** is the line indented inside a `func`? Local.
23
24
## C621 — Local variables
25
26
**Definition.** Variables defined inside a function that can only be accessed by that function.
27
28
```gdscript
29
func calculate_fare() -> void:
30
# C621 — local variable: only calculate_fare() can see it
31
var fare: float = 5.30
32
balance -= fare
33
```
34
35
Parameters and loop variables are local too — in `connect-go-dots/grid.gd`, the parameter `photo: Texture2D` and the loop variable `button` exist only inside their function.
36
37
## C631 — Global variables
38
39
**Definition.** Variables defined outside any function that can be accessed by all functions throughout the source code.
40
41
At the script level:
42
43
```gdscript
44
extends Control
45
46
# C631 — global variables: every func in this script can use them
47
var balance: float = 20.00
48
var is_concession: bool = false
49
```
50
51
Or using `class_name` with `static` for access from other scripts:
52
53
```gdscript
54
class_name GlobalVars
55
56
static var g_var = 20 # C631 — global via class_name
57
```
58
59
An **autoload singleton** is the Godot-idiomatic project-wide global — if you use one, name it as your C631 evidence in validation.
60
61
**In connect-go-dots** — the autoload in action (`shared.gd`, registered as `Shared`):
62
63
```gdscript
64
# connect-go-dots — shared.gd (autoload "Shared")
65
extends Node
66
67
## Handed from one screen to the next. Lives on root, so a scene change
68
## cannot touch it.
69
var photo: Texture2D # C631 — global: both screens use it
70
```
71
72
```gdscript
73
Shared.photo = photo # C631: grid.gd — one screen writes it
74
%Photo.texture = Shared.photo # C631: detail.gd — the other reads it
75
```
76
77
The `##` comment is model internal documentation: it says *why* the variable lives where it does.
78
79
## C622 — Constants
80
81
**Definition.** A fixed value that, once defined, cannot be altered during the execution of a program.
82
83
```gdscript
84
# C622 — constant: the daily cap never changes while the program runs
85
const DAILY_CAP: float = 9.60
86
```
87
88
**Earns the tick:** `const` used for a value that genuinely never changes, named in CAPITALS. Showing Godot's error when you try to assign to it is a neat validation demo.
89
90
## C628 and C634 — choosing the right data type
91
92
C621/C631 is that the variable **exists**. C628/C634 is that its data type **suits the data** — C628 for locals, C634 for globals.
93
94
```gdscript
95
extends Control
96
97
var trips_today: int = 0 # C634 — int: you cannot take half a trip
98
var balance: float = 20.00 # C634 — float: money needs decimal places
99
var is_concession: bool = false # C634 — bool: only two possible answers
100
var card_id: String = "" # C634 — String: digits never used in a calculation
101
102
func charge(zone: int) -> void:
103
var fare: float = FARE_TABLE[zone] # C628 — float: fares have cents
104
balance -= fare
105
```
106
107
From tile-matching-game (`deck.gd`):
108
109
```gdscript
110
# tile-matching-game — deck.gd
111
var key: String = card["pair"] # C628 — String: the pair label from the CSV
112
```
113
114
**State the data type.** `var trips_today = 0` cannot earn C634 because no data type has been given for the marker to assess. Always write `: int`, `: float`, `: bool` or `: String`.
115
116
`var trips_today := 0` is acceptable — GDScript works out the type for you — but name it in your comment so the marker can see it: `# C634 — int: you cannot take half a trip`.
117
118
Types go beyond `int`/`float`/`bool`/`String`: in connect-go-dots the global is `var photo: Texture2D` — same standard, `# C634 — Texture2D: the value is an image`.
119
120
The **why** in these comments doubles as your reasoning evidence (C629/C638) — see [Data Types](/sd/C06/Data%20Types).
121
122
## Check Your Understanding
123
124
1. `var speed := 5` at script level — which code does it earn as written, and what more would C634 need?
125
126
>| ### Answer
127
>| C631 (a global exists). C634 needs the type visible — write `: int`, or name it in the comment — plus the *why*.
128
129
2. Are function parameters local or global?
130
131
>| ### Answer
132
>| Local (C621): they exist only inside their function.
133
134
3. What three things make a C622 constant?
135
136
>| ### Answer
137
>| `const`, a CAPITALS name, and a value that genuinely never changes while the program runs.