问题
Until Swift 2 I used this extension to remove multiple whitespaces:
func condenseWhitespace() -> String {
let components = self.componentsSeparatedByCharactersInSet(NSCharacterSet.whitespaceAndNewlineCharacterSet()).filter({!Swift.isEmpty($0)})
return " ".join(components)
}
but with Swift 2 now I get the error
Cannot invoke 'isEmpty' with an argument list of type '(String)'
How could I now remove multiple spaces with Swift 2? Thnx!
回答1:
In Swift 2, join
has become joinWithSeparator
and you call it on the array.
In filter
, isEmpty
should be called on the current iteration item $0
.
To replace whitespaces and newline characters with unique space characters as in your question:
extension String {
func condenseWhitespace() -> String {
let components = self.componentsSeparatedByCharactersInSet(NSCharacterSet.whitespaceAndNewlineCharacterSet())
return components.filter { !$0.isEmpty }.joinWithSeparator(" ")
}
}
let result = "Hello World.\nHello!".condenseWhitespace() // "Hello World. Hello!"
Because your function does not take any parameter you could make it a property instead:
extension String {
var condensedWhitespace: String {
let components = self.componentsSeparatedByCharactersInSet(NSCharacterSet.whitespaceAndNewlineCharacterSet())
return components.filter { !$0.isEmpty }.joinWithSeparator(" ")
}
}
let result = "Hello World.\nHello!".condensedWhitespace // "Hello World. Hello!"
In Swift 3 there's even more changes.
Function:
extension String {
func condenseWhitespace() -> String {
let components = self.components(separatedBy: NSCharacterSet.whitespacesAndNewlines)
return components.filter { !$0.isEmpty }.joined(separator: " ")
}
}
let result = "Hello World.\nHello!".condenseWhitespace()
Property:
extension String {
var condensedWhitespace: String {
let components = self.components(separatedBy: NSCharacterSet.whitespacesAndNewlines)
return components.filter { !$0.isEmpty }.joined(separator: " ")
}
}
let result = "Hello World.\nHello!".condensedWhitespace
In Swift 4.2 NSCharacterSet is now CharacterSet, and you can omit and use dot syntax:
extension String {
func condenseWhitespace() -> String {
let components = self.components(separatedBy: .whitespacesAndNewlines)
return components.filter { !$0.isEmpty }.joined(separator: " ")
}
}
let result = "Hello World.\nHello!".condenseWhitespace() // "Hello World. Hello!"
回答2:
Split string to array and then join again in not memory efficient. Its Takes lot of memory. The best way in this case is to scan the given string and perform operations on that. Regular Expression is the advance way to scan a text. For the above conclusion the the solution is given below:
Swift 4.x
extension String {
func removeExtraSpaces() -> String {
return self.replacingOccurrences(of: "[\\s\n]+", with: " ", options: .regularExpression, range: nil)
}
}
Usages
let startingString = "hello world! \n\n I am here!"
let processedString = startingString.removeExtraSpaces()
print(processedString)
Output:
processedString => "hello world! I am here!"
You can Do more according to your own requirements but thing I am pointing out here is to use regular expressions with string rather then create arrays which will consume lot of memory.
回答3:
SWIFT 3: Cleaner version
extension String {
var condensedWhitespace: String {
let components = self.components(separatedBy: .whitespacesAndNewlines)
return components.filter { !$0.isEmpty }.joined(separator: " ")
}
}
回答4:
Here is mine: How it's actually worked.
extension String {
func removeExtraSpaces() -> String {
var data = ""
var numberOfSpace = 0
let items = self.getComponents(separatedBy: " ")
for item in items{
if item == " "{
numberOfSpace = numberOfSpace + 1
}else{
numberOfSpace = 0
}
if numberOfSpace == 1 || numberOfSpace == 0 {
data = data + item
//data.append(item)
}
}
return data
}
}
Usages
var message = "What is the purpose of life?"
message = message.removeExtraSpaces()
print(message)
Output:
What is the purpose of life?
回答5:
var str = "Hello World.\nHello!"
if let regex = try? NSRegularExpression(pattern: "\\s+", options:NSRegularExpression.Options.caseInsensitive)
{
str = regex.stringByReplacingMatches(in: str, options: [], range: NSMakeRange(0, str.count), withTemplate: " ")
}
来源:https://stackoverflow.com/questions/33058676/how-to-remove-multiple-spaces-in-strings-with-swift-2