How to pass global variables through switch/case - swift

Question

I realise this has been asked before, but the answer here (to declare the variable outside the block) doesn't seem to work.
link description
var filter: String
func Usage() {
print("Usage: <filter> <input> [output]")
print("System filter paths do not need to be specified.")
return
}
let arguments = ["qwe", "value", "qwe", "asd"]
print(arguments.count)
switch arguments.count {
case 1:
Usage()
case 2:
Usage()
case 3:
filter = arguments[1]
default:
filter = arguments[1]
print (filter)
}
print (filter)
I get "value" in Xcode's playground for the first print, but the second gives "\n" or "value not initialized".
What am I doing wrong?

Answer 1

Your code won´t compile first of all, you do get the error error: variable 'filter' used before being initialized
So declare filter as follow:
var filter = String() or var filter = ""
Secondly since you´re not adding all of your code I tried the following:
var filter = String()
let x = 0
switch x {
case 1:
print("1")
default:
filter = "value"
print(filter)
}
print(filter)
This prints out:
value
value
If you need further help update your question with more information.
Update:
Just tried your updated code:
var filter = String()
let arguments = ["qwe", "value", "qwe", "asd"]
print(arguments.count)
switch arguments.count {
case 1:
break
case 2:
break
case 3:
filter = arguments[1]
default:
filter = arguments[1]
print (filter)
}
print (filter)
And this prints out:
4
value
value
Which is exactly what it should print out. Remember the initialization of filter.
Update 2:
This is what you´re trying to do, your other result was always return 4 because that´s the count of arguments. Try the below code instead.
var filter = String()
func Usage() {
print("Usage: <filter> <input> [output]")
print("System filter paths do not need to be specified.")
return
}
let arguments = ["qwe", "value", "qwe", "asd"]
print(arguments.count)
for i in 0..<arguments.count {
switch i {
case 0:
Usage()
case 1:
Usage()
case 2:
Usage()
case 3:
filter = arguments[1]
default:
filter = arguments[1]
print (filter)
}
}
print (filter)
This prints out:
4
Usage: <filter> <input> [output]
System filter paths do not need to be specified.
Usage: <filter> <input> [output]
System filter paths do not need to be specified.
Usage: <filter> <input> [output]
System filter paths do not need to be specified.
value

Answer 2

Your code seems to be an entry point for a command line interface.
This is an alternative approach without declaring a global variable and without a switch.
Usage is printed if the number of arguments is less than 3 otherwise the first two arguments after the name of CLI (at index 0) are assigned to two variables.
let arguments = ["qwe", "value", "qwe", "asd"]
print(arguments.count)
if arguments.count < 3 {
Usage()
exit(EXIT_FAILURE)
}
let filter = arguments[1]
let secondArgument = arguments[2]
print (filter, secondArgument)
Then you could switch over the filter
switch filter {
case "value": doThis(with: secondArgument)
case "someOtherFilter": doThat(with: secondArgument)
default: doNothing()
}