将字符串截断为特定长度

如果你已经输入了一段句子/文本，你想只保存指定长度的文本。将以下扩展添加到类中

extension String {

   func trunc(_ length: Int) -> String {
    if self.characters.count > length {
        return self.substring(to: self.characters.index(self.startIndex, offsetBy: length))
    } else {
        return self
    }
  }

  func trim() -> String{
     return self.trimmingCharacters(in: CharacterSet.whitespacesAndNewlines)
   }

}

Use

var str = "Lorem Ipsum is simply dummy text of the printing and typesetting industry."
//str is length 74
print(str)
//O/P:  Lorem Ipsum is simply dummy text of the printing and typesetting industry.

str = str.trunc(40)
print(str)
//O/P: Lorem Ipsum is simply dummy text of the 

//Swift 4.0删除空格和新行

extension String {
    func trim() -> String {
        return self.trimmingCharacters(in: .whitespacesAndNewlines)         
    }
}

你可以在我写的Swift String扩展https://bit.ly/JString中使用trim()方法。

var string = "hello  "
var trimmed = string.trim()
println(trimmed)// "hello"

另一种类似的方式:

extension String {
    var trimmed:String {
        return self.trimmingCharacters(in: CharacterSet.whitespaces)
    }
}

使用:

let trimmedString = "myString ".trimmed

Swift 5和4.2

let trimmedString = " abc ".trimmingCharacters(in: .whitespaces)
 //trimmedString == "abc"

下面介绍如何从字符串的开头和结尾删除所有空白。

(用Swift 2.0测试的示例。)

let myString = "  \t\t  Let's trim all the whitespace  \n \t  \n  "
let trimmedString = myString.stringByTrimmingCharactersInSet(
    NSCharacterSet.whitespaceAndNewlineCharacterSet()
)
// Returns "Let's trim all the whitespace"

(用Swift 3+测试的示例。)

let myString = "  \t\t  Let's trim all the whitespace  \n \t  \n  "
let trimmedString = myString.trimmingCharacters(in: .whitespacesAndNewlines)
// Returns "Let's trim all the whitespace"