Control Flow : Swift tutorial

Swift Provides diffrent type of controll flow statements like:

  • Loops Statements : Loops are used for perform the task multiple times or for handel the arays, dictionaries, string etc
  • Conditional Statements : Execute some line of code at certain condition.
  • Control Transfer Statements : Change the order in which your code is executed, by transferring control from one piece of code to another.

Loops Statements

  • Loops are used for execute Number of line of code multiple times/statement is execute sequentially. This execution is depending on condtions is true/false.
  • Swift have these loopes statement
    • For-In loops
    • While loop
    • Repeat-While loop
1. For-In loop

For-In loop is used when we need to execute set of code at certain number of time in repeated manner.
For-In loop in swift syntax are following :

for item in Range {
    Statement
}
  • Uses a for-in loop to iterate over the items in an array :
let names = ["A", "B", "C", "D"]
for name in names { 
print("Show, \(name)!")
}
/* outpout:-
 Show, A!
 Show, B!
 Show, C!
 Show, D! */        
  • Uses Half upper Range operator (..<) to include lowwer bound but not upper bound. By this operator we can run for loop at perticular range. We can follow this with other range operators also like “One-Sided Ranges(...14...)”, “Closed Range Operator(1...5)”
 for item in 2..<names.count {
 print("Show, \(item)!")
 }
 //Output
/* Output :-
 Show, 2!
 Show, 3!
 Show, 4! */
  • If you don’t need each value from a sequence, you can ignore the values by using an underscore in place of a variable name.
let base = 3
let power = 10
var answer = 1
for _ in 1...power {
    answer *= base
}
print("\(base) to the power of \(power) is \(answer)")
// Prints "3 to the power of 10 is 59049"
  • use with stride(from:to:by:), Its use for a constant gap between in sequence. And it return the sequence starting value but not end value.
 swiftlet minutes = 60
 let minuteInterval = 5
 for tickMark in stride(from: 0, to: minutes, by: minuteInterval) {
 print("Show, \(tickMark)!")
 }
 //Output:- 
 // render the tick mark every 5 minutes (0, 5, 10, 15 ... 45, 50, 55)
  • We can also use For-In loop with dictionary. Each item of dictionary is getting in (key, value)pair.
 let numberOfLegs = ["dog": 8, "ant": 6, "cat": 4]
 for (animalName, legCount) in numberOfLegs {
 print("\(animalName)s have \(legCount) legs")
 }
 /* Output:-
ants have 6 legs
cats have 4 legs
dogs have 8 legs */
2. While loop

while loop performs a set of statements until a condition becomes false. While loop is used when we not know the number of Running of set of statement before first execution begin.
While loop in swift syntax are following :

while condition {
    statements
}

while loop starts by evaluating a single condition. If the condition is true, a set of statements is repeated until the condition becomes false.

var number = 10
var sum = 0
while number != 0 {
    sum = sum + number
    number = number - 1
}
print(sum)
//Output: - 55
3. repeat-while loop

The other variation of the while loop, known as the repeat-while loop, performs a single pass through the loop block first, before considering the loop’s condition. It then continues to repeat the loop until the condition is false.
repeat-while loop in swift syntax are following :

repeat {
    statements
} while condition
number = 10
repeat {
   print(number)
   number = number - 1
} while number > 0
/* Output: -
10
9
8
7
6
5
4
3
2
1 */

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