How to remove whitespaces in strings in Swift?

问题:

This works

let replaced = String(map(aString.generate()) {
    $0 == " " ? "-" : $0 })

and this doesn't

let replaced = String(map(aString.generate()) {
    $0 == " " ? "" : $0 })

Why?

回答1:

Enumerating a string gives a sequence of characters, so $0 inside the closure has the type Character. This compiles

{ $0 == " " ? "-" : $0 }

because "-" in this context is interpreted as a character literal and therefore of the same type as $0. But

{ $0 == " " ? "" : $0 }

does not compile because "" is not a character literal (and in the conditional expression a ? b : c the operands b and c must have the same type).

You can fix that by converting $0 to a string:

{ $0 == " " ? "" : String($0) }

but now the mapping returns an array of strings instead of an array of characters. So instead of the String() constructor you have to join the results:

let replaced = "".join(map(aString) { $0 == " " ? "" : String($0) })
// Swift 2 / Xcode 7:
let replaced = "".join(aString.characters.map({ $0 == " " ? "" : String($0) }))

(Note that calling generate() explicitly is not needed.)

Of course the same result would also be achieved with

// Before Swift 3.0
let replaced = aString.stringByReplacingOccurrencesOfString(" ", withString: "")

// After Swift 3.0
let replaced = aString.replacingOccurrences(of: " ", with: "")

回答2:

For Swift 5:

" spaces here ".replacingOccurrences(of: " ", with: "")

returns:

"spaceshere"

回答3:

If you want to remove white space from string then just pass string with stringByReplacingOccurrencesOfString function like below,

let replacedString = string.replacingOccurrences(of: " ", with: "")

For Text Fields, you can apply directly object of UITextField,

let replacedString = textField.text!.replacingOccurrences(of: " ", with: "")

回答4:

This should work as of Swift 2.2:

let replaced = String(aString.characters.filter {$0 != " "})

回答5:

You are mapping thus the number of elements should be preserved. In the second case you remove elements. Your example will fail even in case you replace " " with --.

You might prefer using filter:

let replaced = String(filter(aString.generate()) { $0 != " "})

回答6:

If you want to delete whitespaces before and after a string, which is very useful in user input forms, you can use:

let replaced = aString.stringByTrimmingCharactersInSet(NSCharacterSet.whitespaceCharacterSet())

You can apply it directly on a textfield as well.

回答7:

If you want to remove all whitespaces anywhere in the String I did come up with this solution for Swift 3.0:

let number = "+000 000 000"
let nonWhiteCharacters = number.unicodeScalars.filter {
    false == NSCharacterSet.whitespacesAndNewlines.contains($0)
}.map(Character.init)
let whitespacelessNumber = String(nonWhiteCharacters)

or even better (you will need generic extension on Sequence):

extension Sequence {
    public func reduce<Result>(_ result: (Self) throws -> Result) rethrows -> Result {
        return try result(self)
    }
}

and then you can write:

let whitespacelessNumber = number.unicodeScalars.filter {
    false == NSCharacterSet.whitespacesAndNewlines.contains($0)
}.map(Character.init).reduce { String($0) }

where you can also replace NSCharacterSet.whitespacesAndNewlines for any of other character sets:

NSCharacterSet.controlCharacters
NSCharacterSet.whitespaces
NSCharacterSet.whitespacesAndNewlines
NSCharacterSet.decimalDigits
NSCharacterSet.letters
NSCharacterSet.lowercaseLetters
NSCharacterSet.uppercaseLetters
NSCharacterSet.nonBaseCharacters
NSCharacterSet.alphanumerics
NSCharacterSet.decomposables
NSCharacterSet.illegalCharacters
NSCharacterSet.punctuationCharacters
NSCharacterSet.capitalizedLetters
NSCharacterSet.symbols
NSCharacterSet.newline

回答8:

try this one:

let strArray0 = strArray1.map { $0.stringByTrimmingCharactersInSet(.whitespaceAndNewlineCharacterSet()) }

Hope this helps

回答9:

None of the previous answers where Swifty enough for me, so I ended up with this using Swift 5:

let nonWhitespaceString = String(whitespaceString.compactMap({ $0.isWhitespace ? nil : $0 })

回答10:

In Swift 3.0 DO as

func RemoveWhiteSpace(aString:String) -> String
    {
        let replaced = aString.trimmingCharacters(in: NSCharacterSet.whitespaces)
        return replaced
    }

And use like this

let nonWhiteSpaceStr = self.RemoveWhiteSpace(aString: "I have white Space        ")