Checking for whitespace in a string typed array - Swift - swift

Question

In a string typed array how can I achieve the functionality as I would for checking whitespace in a string? I'd like to check if the array contains only whitespace
var stringExample: String!
var stringArrayExample: [String]!
if stringExample.trimmingCharacters(in: .whitespaces).isEmpty{
//string contains whitespace characters
}

Answer 1

Swift 3 would look something like this if I'm understanding what you're wanting:
var someStrings = [" ", "foo", "bar", "\t"]
let result = someStrings.filter { $0.trimmingCharacters(in: .whitespacesAndNewlines).isEmpty }
print(result) // [" ", "\t"]
If you're just wanting to know if the array of strings are all whitespace-only strings you could change the last two lines to:
let result = someStrings.filter { $0.trimmingCharacters(in: .whitespacesAndNewlines).isEmpty == false }
print(result.isEmpty) // false
Note that both these use .whitespacesAndNewlines if you don't want new lines, just use .whitespaces like you do in your original example.

Answer 2

I've created an extension for String which returns whether it's empty or contains only whitespace:
extension String {
var isEmptyOrWhitespace : Bool {
return self.trimmingCharacters(in: .whitespaces).isEmpty
}
}
And since I'm also a .NET developer and like the methods Any, All etc. I've also created an extension for the Array type, which lets me check a condition for every element in the array, leveraging the reduce function:
extension Array {
func all(test: (Element) -> Bool) -> Bool {
return self.reduce(true) { $0 && test($1) }
}
}
Then you can combine these two to get a fairly nice syntax, which is also fairly performant, since it "breaks" when it stumbles upon an element that does not comply with the provided test (using a for instead of reduce would probably be even more efficient).
let strings1 = [" ", "", "\t"]
print(strings1.all { $0.isEmptyOrWhitespace }) // true
print(strings1.all { !$0.isEmptyOrWhitespace }) // false
By printing within the test, you can see it no longer executes the tests for elements when it finds the first non-compliant one.
let strings2 = [" ", "x", "\t"]
print(strings2.all(test: { (str) -> Bool in
let e = str.isEmptyOrWhitespace
print ("[\(str)]: \(e)")
return e
}))
Prints:
[ ]: true
[x]: false
false