Why should I create a variable outside of switch/case?
For example this code will have an error Cannot find 'size' in scope:
func sizeCheckNoVar(value: Int) -> String {
switch value {
case 0...2:
let size = "small"
case 3...5:
let size = "medium"
case 6...10:
let size = "large"
default:
let size = "huge"
}
return size
}
There is a default condition and AFIK all options are covered.
In the same time this code will be fine:
func sizeCheckVar(value: Int) -> String {
var size: String
switch value {
case 0...2:
size = "small"
case 3...5:
size = "medium"
case 6...10:
size = "large"
default:
size = "huge"
}
return size
}
PS I saw this question Cannot find variable in scope , but I want to know why instead of how to avoid
A pair of braces is called a scope.
In Swift (unlike some other languages) there is a simple but iron rule:
A variable declared inside a scope – in your particular case inside the switch statement – is visible in its own scope and on a lower level – like in your second example
It's not visible on a higher level outside the scope – like in your first example.
You can even declare size as constant because it's guaranteed to be initialized.
func sizeCheckVar(value: Int) -> String {
let size: String
switch value {
case 0...2: size = "small"
case 3...5: size = "medium"
case 6...10: size = "large"
default: size = "huge"
}
return size
}
However actually you don't need the local variable at all. Just return the values immediately
func sizeCheckVar(value: Int) -> String {
switch value {
case 0...2: return "small"
case 3...5: return "medium"
case 6...10: return "large"
default: return "huge"
}
}
Side note: The colon in a switch statement is also a kind of scope separator otherwise you would get errors about redeclaration of variables in the first example.