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Swift Language Basic conditionals: if-statements


Example

An if statement checks whether a Bool condition is true:

let num = 10

if num == 10 {
    // Code inside this block only executes if the condition was true.
    print("num is 10")
}

let condition = num == 10   // condition's type is Bool
if condition {
    print("num is 10")
}

if statements accept else if and else blocks, which can test alternate conditions and provide a fallback:

let num = 10
if num < 10 {  // Execute the following code if the first condition is true.
    print("num is less than 10")
} else if num == 10 {  // Or, if not, check the next condition...
    print("num is 10")
} else {  // If all else fails...
    print("all other conditions were false, so num is greater than 10")
}

Basic operators like && and || can be used for multiple conditions:

The logical AND operator

let num = 10
let str = "Hi"
if num == 10 && str == "Hi" {
    print("num is 10, AND str is \"Hi\"")
}

If num == 10 was false, the second value wouldn't be evaluated. This is known as short-circuit evaluation.

The logical OR operator

if num == 10 || str == "Hi" {
    print("num is 10, or str is \"Hi\")
}

If num == 10 is true, the second value wouldn't be evaluated.

The logical NOT operator

if !str.isEmpty {
    print("str is not empty")
}