Swift Constants

Constants in Swift Language

In Swift, constants are used to store data that should not change during the execution of a program. Unlike variables, constants have fixed values that cannot be modified after being set. These are essential for ensuring code safety and predictability.

Constants are declared using the let keyword. They are ideal for values that should remain fixed throughout the program, such as mathematical constants or configuration settings.

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Example 1: Declaring and Using Constants

This program demonstrates how to declare constants and use them in calculations:

File: main.swift

let gravity = 9.8
let mass = 50.0

// Calculate weight using the formula: weight = mass * gravity
let weight = mass * gravity

print("Mass: \(mass) kg")
print("Gravity: \(gravity) m/s²")
print("Weight: \(weight) N")

Explanation:

• gravity is declared as a constant with the value 9.8 (the acceleration due to gravity).
• mass is another constant with a value of 50.0 kilograms.
• The weight is calculated by multiplying mass and gravity.
• The print statements display the values of mass, gravity, and weight.

Output:

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Example 2: Using Constants for Immutable Values

This example highlights the immutability of constants:

File: main.swift

let pi = 3.14159
print("Value of pi: \(pi)")

//updating the constant raises error
pi = 3.14

Explanation:

• pi is declared as a constant with the value 3.14159.
• Since pi is a constant, attempting to modify it (as shown in the commented-out line) will result in a compile-time error.

Output:

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Example 3: Constants and Variables Together

This program demonstrates how constants and variables can be used together:

File: main.swift

let base = 10
var height = 5

// Calculate the area of a rectangle using the formula: area = base * height
let area = base * height

print("Base: \(base)")
print("Height: \(height)")
print("Area: \(area)")

// Update the height and recalculate the area
height = 7
let newArea = base * height
print("New Height: \(height)")
print("New Area: \(newArea)")

Explanation:

• base is declared as a constant because its value does not change.
• height is a variable because its value is updated later in the program.
• The area is calculated using the initial values of base and height.
• The height is updated to a new value, and the area is recalculated to reflect the change.

Output:

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Benefits of Using Constants

Using constants improves the clarity and safety of your code:

• Immutability: Constants prevent accidental modifications to critical values.
• Readability: Constants convey intent by making it clear which values should remain unchanged.
• Optimization: The Swift compiler can optimize code with constants more effectively.

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Conclusion

Constants are a key feature in Swift programming, enabling you to create safer and more predictable code. Use let for values that should not change.