How do I concatenate strings in Swift?

问题

How to concatenate string in Swift?

In Objective-C we do like

NSString *string = @\"Swift\";
NSString *resultStr = [string stringByAppendingString:@\" is a new Programming Language\"];

NSString *resultStr=[NSString stringWithFormat:@\"%@ is a new Programming Language\",string];

But I want to do this in Swift-language.

回答1:

You can concatenate strings a number of ways:

let a = "Hello"
let b = "World"

let first = a + ", " + b
let second = "\(a), \(b)"

You could also do:

var c = "Hello"
c += ", World"

I'm sure there are more ways too.

Bit of description

let creates a constant. (sort of like an NSString). You can't change its value once you have set it. You can still add it to other things and create new variables though.

var creates a variable. (sort of like NSMutableString) so you can change the value of it. But this has been answered several times on Stack Overflow, (see difference between let and var).

Note

In reality let and var are very different from NSString and NSMutableString but it helps the analogy.

回答2:

You can add a string in these ways:

str += ""
str = str + ""
str = str + str2
str = "" + ""
str = "\(variable)"
str = str + "\(variable)"

I think I named them all.

回答3:

var language = "Swift" 
var resultStr = "\(language) is a new programming language"

回答4:

This will work too:

var string = "swift"
var resultStr = string + " is a new Programming Language"

回答5:

\ this is being used to append one string to another string.

var first = "Hi" 
var combineStr = "\(first) Start develop app for swift"

You can try this also:- + keyword.

 var first = "Hi" 
 var combineStr = "+(first) Start develop app for swift"

Try this code.

回答6:

let the_string = "Swift"
let resultString = "\(the_string) is a new Programming Language"

回答7:

Very Simple:

let StringA = "Hello"
let StringB = "World"
let ResultString = "\(StringA)\(StringB)"
println("Concatenated result = \(ResultString)")

回答8:

You can now use stringByAppendingString in Swift.

var string = "Swift"
var resultString = string.stringByAppendingString(" is new Programming Language")

回答9:

Xcode didn't accept optional strings added with a normal string. I wrote this extensions to solve that problem:

extension String {
    mutating func addString(str: String) {
        self = self + str
    }
}

Then you can call it like:

var str1: String?
var str1 = "hi"
var str2 = " my name is"
str1.addString(str2)
println(str1) //hi my name is

However you could now also do something like this:

var str1: String?
var str1 = "hi"
var str2 = " my name is"
str1! += str2

回答10:

It is called as String Interpolation. It is way of creating NEW string with CONSTANTS, VARIABLE, LITERALS and EXPRESSIONS. for examples:

      let price = 3
      let staringValue = "The price of \(price) mangoes is equal to \(price*price) "

also

let string1 = "anil"
let string2 = "gupta"
let fullName = string1 + string2  // fullName is equal to "anilgupta"
or 
let fullName = "\(string1)\(string2)" // fullName is equal to "anilgupta"

it also mean as concatenating string values.

Hope this helps you.

回答11:

To print the combined string using

Println("\(string1)\(string2)")

or String3 stores the output of combination of 2 strings

let strin3 = "\(string1)\(string2)"

回答12:

One can also use stringByAppendingFormat in Swift.

var finalString : NSString = NSString(string: "Hello")
finalString = finalString.stringByAppendingFormat("%@", " World")
print(finalString) //Output:- Hello World
finalString = finalString.stringByAppendingFormat("%@", " Of People")
print(finalString) //Output:- Hello World Of People

回答13:

You could use SwiftString (https://github.com/amayne/SwiftString) to do this.

"".join(["string1", "string2", "string3"]) // "string1string2string"
" ".join(["hello", "world"]) // "hello world"

DISCLAIMER: I wrote this extension

回答14:

Swift 4.2

You can also use an extension:

extension Array where Element == String? {
    func compactConcate(separator: String) -> String {
        return self.compactMap { $0 }.filter { !$0.isEmpty }.joined(separator: separator)
    }
}

Use:

label.text = [m.firstName, m.lastName].compactConcate(separator: " ")

Result:

"The Man"
"The"
"Man"

回答15:

From: Matt Neuburg Book “iOS 13 Programming Fundamentals with Swift.” :

To combine (concatenate) two strings, the simplest approach is to use the + operator:

let s = "hello"
let s2 = " world"
let greeting = s + s2

This convenient notation is possible because the + operator is overloaded: it does one thing when the operands are numbers (numeric addition) and another when the operands are strings (concatenation). The + operator comes with a += assignment shortcut; naturally, the variable on the left side must have been declared with var:

var s = "hello"
let s2 = " world"
s += s2

As an alternative to +=, you can call the append(_:) instance method:

var s = "hello"
let s2 = " world"
s.append(s2)

Another way of concatenating strings is with the joined(separator:) method. You start with an array of strings to be concatenated, and hand it the string that is to be inserted between all of them:

let s = "hello"
let s2 = "world"
let space = " "
let greeting = [s,s2].joined(separator:space)

回答16:

I just switched from Objective-C to Swift (4), and I find that I often use:

let allWords = String(format:"%@ %@ %@",message.body!, message.subject!, message.senderName!)

回答17:

In Swift 5 apple has introduces Raw Strings using # symbols.

Example:

print(#"My name is "XXX" and I'm "28"."#)
let name = "XXX"
print(#"My name is \#(name)."#)

symbol # is necessary after \. A regular \(name) will be interpreted as characters in the string.

来源：https://stackoverflow.com/questions/24034174/how-do-i-concatenate-strings-in-swift

标签

string

swift

concat

string-concatenation