Practice

Swift exercises

Make a change, predict what it will do, and compare the result.

1
Swift Basics
Bind a constant and print it.
Adapt the lesson example. Change one value or element, predict the result, and explain why it changes.
Review lesson →
Show starting example
Swift
```
let name = "Ada"
print("Hello, \(name)")
```
2
Swift Functions and Argument Labels
Use default values and argument labels to make calls readable.
Predict greet("Cy", times: 0).
Reveal answer and reasoning
It returns an empty string, so print writes an empty line.
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Show starting example
Swift
```
func greet(_ name: String, times: Int = 1) -> String {
    return Array(repeating: "Hi \(name)!", count: times).joined(separator: " ")
}

print(greet("Ada"))
print(greet("Bo", times: 2))
```
3
Swift Optionals
Handle values that might be missing with if let.
Give failed conversions a default of 0.
Reveal answer and reasoning
Use let number = Int(text) ?? 0 and print number + 1 for every entry.
Review lesson →
Show starting example
Swift
```
let values = ["42", "x7"]
for text in values {
    if let number = Int(text) {
        print("number \(number + 1)")
    } else {
        print("not a number: \(text)")
    }
}
```
4
Swift Structs
Model data with a struct, which is copied when assigned.
Predict the second result if y were set to 0 instead of x to 6.
Reveal answer and reasoning
The second call returns 9 + 0 = 9.
Review lesson →
Show starting example
Swift
```
struct Point {
    var x: Int
    var y: Int

    func distanceSquared() -> Int {
        return x * x + y * y
    }
}

var point = Point(x: 3, y: 4)
print(point.distanceSquared())
point.x = 6
print(point.distanceSquared())
```
5
Swift Arrays
Grow an array and combine its values with reduce.
Use max() to find the highest score.
Reveal answer and reasoning
scores.max() returns an optional, Optional(95), because an empty array has no maximum.
Review lesson →
Show starting example
Swift
```
var scores = [82, 91, 76]
scores.append(95)
let total = scores.reduce(0, +)
print(scores.count, total)
```

Swift Basics

Swift Functions and Argument Labels

Swift Optionals

Swift Structs

Swift Arrays