试试这个:

let categories = dictData?.value(forKeyPath: "listing_subcategories_id") as! NSMutableArray
                        let tempArray = NSMutableArray()
                        for dc in categories
                        {
                            let dictD = dc as? NSMutableDictionary
                            tempArray.add(dictD?.object(forKey: "subcategories_name") as! String)
                        }
                        let joinedString = tempArray.componentsJoined(by: ",")

如果数组包含字符串，你可以使用String的join方法:

var array = ["1", "2", "3"]

let stringRepresentation = "-".join(array) // "1-2-3"

在Swift 2中:

var array = ["1", "2", "3"]

let stringRepresentation = array.joinWithSeparator("-") // "1-2-3"

如果您想使用特定的分隔符(连字符、空格、逗号等)，这可能很有用。

否则，你可以简单地使用description属性，它返回数组的字符串表示形式:

let stringRepresentation = [1, 2, 3].description // "[1, 2, 3]"

提示:任何实现Printable协议的对象都有一个description属性。如果你在自己的类/结构中采用该协议，你也可以使它们打印友好

在Swift 3中

join变为joined，示例[nil， "1"， "2"].flatMap({$0}).joined() joinWithSeparator变成了joined(separator:)(仅适用于字符串数组)

在Swift 4中

var array = ["1", "2", "3"]
array.joined(separator:"-")

使用Swift 5，根据您的需要，您可以选择以下Playground示例代码之一来解决您的问题。

将字符数组转换为不带分隔符的字符串:

let characterArray: [Character] = ["J", "o", "h", "n"]
let string = String(characterArray)

print(string)
// prints "John"

将String数组转换为不带分隔符的String:

let stringArray = ["Bob", "Dan", "Bryan"]
let string = stringArray.joined(separator: "")

print(string) // prints: "BobDanBryan"

将字符串数组转换为单词之间带有分隔符的字符串:

let stringArray = ["Bob", "Dan", "Bryan"]
let string = stringArray.joined(separator: " ")

print(string) // prints: "Bob Dan Bryan"

将字符串数组转换为字符之间带有分隔符的字符串:

let stringArray = ["car", "bike", "boat"]
let characterArray = stringArray.flatMap { $0 }
let stringArray2 = characterArray.map { String($0) }
let string = stringArray2.joined(separator: ", ")

print(string) // prints: "c, a, r, b, i, k, e, b, o, a, t"

将float数组转换为数字之间带有分隔符的String:

let floatArray = [12, 14.6, 35]
let stringArray = floatArray.map { String($0) }
let string = stringArray.joined(separator: "-")

print(string)
// prints "12.0-14.6-35.0"

修改一个可选/非可选字符串数组

//Array of optional Strings
let array : [String?] = ["1",nil,"2","3","4"]

//Separator String
let separator = ","

//flatMap skips the nil values and then joined combines the non nil elements with the separator
let joinedString = array.flatMap{ $0 }.joined(separator: separator)


//Use Compact map in case of **Swift 4**
    let joinedString = array.compactMap{ $0 }.joined(separator: separator

print(joinedString)

这里是flatMap, compactMap跳过数组中的nil值，并附加其他值以给出一个连接字符串。

当你也有struct数组时，你可以使用joined()来获得单个String。

struct Person{
    let name:String
    let contact:String
}

使用map() & joined()可以轻松生成字符串

PersonList.map({"\($0.name) - \($0.contact)"}).joined(separator: " | ")

输出:

Jhon - 123 | Mark - 456 | Ben - 789  

let arrayTemp :[String] = ["Mani","Singh","iOS Developer"]
    let stringAfterCombining = arrayTemp.componentsJoinedByString(" ")
   print("Result will be >>>  \(stringAfterCombining)")

结果将>>> Mani Singh iOS开发者