如何在Swift 5中检查字符串是否包含多个字符

Question

I have a failure initializer that takes a string, if this string contains incorrect characters (T, A, C, G) I want to return nil:

I tried something like this, unsuccessful:

init?(strand: String) {
    let success = strand.contains(where:  { !"TACG".contains($0) })
    if !success {
        return nil
    }

    self.strand = strand
}

I somehow got confused by the two contains calls, so I am not sure if my check is correct.
Any help is appreciated.

Answer 1

In this case I'd prefer the API rangeOfCharacter(from which checks the string against a character set

init?(strand: String) {
    guard strand.rangeOfCharacter(from: CharacterSet(charactersIn: "TACG")) == nil else { return nil }
    self.strand = strand
}

Answer 2

If you don't want to import Foundation you can also use Collection method allSatisfy

func allSatisfy(_ predicate: (Character) throws -> Bool) rethrows -> Bool

And make sure your string contains all characters

let allSatisfy = "CGAT".allSatisfy("TACG".contains)
print(allSatisfy)  // true

Answer 3

Just move the ! placement, check out the code below .

 init?(strand: String) {
    let success = !strand.contains(where:  { "TACG".contains($0) }) 
    if !success {
        return nil
    }
    self.strand = strand
}