Swift - For-in Loop

Swift - For-in Loop

In Swift, the for-in loop is a powerful construct used to iterate over a sequence, such as items in an array, characters in a string, or even key-value pairs in a dictionary. It provides a concise way to run a set of statements for each item in a collection.

1. Iterating Over an Array:

let numbers = [1, 2, 3, 4, 5] for number in numbers { print(number) } // Outputs: // 1 // 2 // 3 // 4 // 5

2. Iterating Over a Dictionary:

let fruitColors: [String: String] = ["apple": "red", "banana": "yellow", "grape": "purple"] for (fruit, color) in fruitColors { print("\(fruit) is \(color)") } // Outputs (order may vary because dictionaries are unordered): // apple is red // banana is yellow // grape is purple

3. Iterating Over a Range:

for index in 1...5 { print(index) } // Outputs: // 1 // 2 // 3 // 4 // 5

4. Iterating Over a String's Characters:

let word = "Swift" for character in word { print(character) } // Outputs: // S // w // i // f // t

5. Ignoring the Current Value:

If you don't need the current item of the sequence, you can use an underscore (_) to ignore it:

for _ in 1...3 { print("Hello") } // Outputs: // Hello // Hello // Hello

6. Using Where to Filter Items:

You can use the where clause in a for-in loop to filter items:

let numbers = [1, 2, 3, 4, 5, 6] for number in numbers where number % 2 == 0 { print(number) } // Outputs: // 2 // 4 // 6

7. Nested for-in Loops:

You can nest for-in loops to iterate over multiple collections:

for i in 1...3 { for j in 1...3 { print("i: \(i), j: \(j)") } }

In Summary:

The for-in loop in Swift is a versatile and essential construct for iteration. It offers a concise way to iterate over a wide variety of sequences and collections, making your code more readable and expressive.

Examples

  1. How to iterate over arrays with for-in in Swift:

    • Description: Use the for-in loop to iterate over elements in an array.

    • Code:

      let numbers = [1, 2, 3, 4, 5] for number in numbers { print(number) }

  2. Looping through dictionaries using for-in in Swift:

    • Description: for-in can iterate over key-value pairs in a dictionary.

    • Code:

      let person = ["name": "John", "age": 30, "city": "New York"] for (key, value) in person { print("\(key): \(value)") }

  3. Swift for-in loop with ranges:

    • Description: Ranges can be used with for-in loops to iterate over a specific range of values.

    • Code:

      for i in 1...5 { print(i) }

  4. Enumerating elements with for-in loop in Swift:

    • Description: The enumerated() method allows access to both the index and the value during iteration.

    • Code:

      let fruits = ["Apple", "Banana", "Orange"] for (index, fruit) in fruits.enumerated() { print("\(index): \(fruit)") }

  5. Using for-in to loop through strings in Swift:

    • Description: Strings can be iterated character by character using for-in.

    • Code:

      let message = "Hello, Swift!" for char in message { print(char) }

  6. Iterating over sets with for-in loop in Swift:

    • Description: Sets can be iterated using for-in to access unique elements.

    • Code:

      let uniqueNumbers: Set<Int> = [1, 2, 3, 2, 4] for number in uniqueNumbers { print(number) }

  7. Nested for-in loops in Swift:

    • Description: for-in loops can be nested to iterate over multiple levels of data.

    • Code:

      let matrix = [[1, 2, 3], [4, 5, 6], [7, 8, 9]] for row in matrix { for element in row { print(element) } }

  8. Break and continue statements in Swift for-in loop:

    • Description: Use break to exit the loop and continue to skip to the next iteration.

    • Code:

      let numbers = [1, 2, 3, 4, 5] for number in numbers { if number == 3 { break // Exit the loop when number is 3 } print(number) }

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