Ruby Constants
A constant is a name written in capital letters. A constant is meant to hold one value that stays fixed.
A constant holds a value
LIMIT is written in capital letters. The puts line prints the value stored in it.
LIMIT = 100
puts LIMITOne value changes, one stays
The variable count changes between the prints. LIMIT prints the same value both times.
LIMIT = 10
count = 1
puts LIMIT
puts count
count = 2
puts LIMIT
puts countChanging a constant warns
The second line stores a new value in LIMIT. Ruby prints a warning, and the program prints no value here.
LIMIT = 5
LIMIT = 9Example
MAX_SCORE = 100
score = 80
puts MAX_SCORE
puts score
score = 90
puts scoreKey points
- A constant is a name meant to stay fixed.
- A constant name starts with a capital letter.
- Constant names in this course use capital letters for the whole name.
- Use = to store a value in a constant.
- Storing a new value in a constant prints a warning.
- The value still changes after the warning.
In this example, MAX_SCORE holds 100. score holds 80, and the next line prints it. score then holds 90, and the last line prints 90.
Note
A warning is not an error, and the program still runs.
Try it Yourself
Edit the code, then press Run.
Running is simulated
Exercise
Which line stores the number 100 in a constant named LIMIT?