我怎样才能得到字符串的第n个字符?我尝试了括号([])访问器,没有运气。
var string = "Hello, world!"
var firstChar = string[0] // Throws error
错误:'下标'是不可用的:不能下标String与Int,请参阅文档注释讨论
我怎样才能得到字符串的第n个字符?我尝试了括号([])访问器,没有运气。
var string = "Hello, world!"
var firstChar = string[0] // Throws error
错误:'下标'是不可用的:不能下标String与Int,请参阅文档注释讨论
当前回答
在Swift 3中,没有对String类的扩展,就像我能做的那样简单!
let myString = "abcedfg"
let characterLocationIndex = myString.index(myString.startIndex, offsetBy: 3)
let myCharacter = myString[characterLocationIndex]
本例中的myCharacter为“3”。
其他回答
这是最好最简单的方法之一
let yourString = "thisString"
print(Array(yourString)[8])
将字符串中的每个字母放入数组 然后选择第9个
斯威夫特4.2
这个答案是理想的,因为它在一个扩展中扩展了String及其所有子序列(Substring)
public extension StringProtocol {
public subscript (i: Int) -> Element {
return self[index(startIndex, offsetBy: i)]
}
public subscript (bounds: CountableClosedRange<Int>) -> SubSequence {
let start = index(startIndex, offsetBy: bounds.lowerBound)
let end = index(startIndex, offsetBy: bounds.upperBound)
return self[start...end]
}
public subscript (bounds: CountableRange<Int>) -> SubSequence {
let start = index(startIndex, offsetBy: bounds.lowerBound)
let end = index(startIndex, offsetBy: bounds.upperBound)
return self[start..<end]
}
public subscript (bounds: PartialRangeUpTo<Int>) -> SubSequence {
let end = index(startIndex, offsetBy: bounds.upperBound)
return self[startIndex..<end]
}
public subscript (bounds: PartialRangeThrough<Int>) -> SubSequence {
let end = index(startIndex, offsetBy: bounds.upperBound)
return self[startIndex...end]
}
public subscript (bounds: CountablePartialRangeFrom<Int>) -> SubSequence {
let start = index(startIndex, offsetBy: bounds.lowerBound)
return self[start..<endIndex]
}
}
使用
var str = "Hello, playground"
print(str[5...][...5][0])
// Prints ","
你也可以像这样将字符串转换为字符数组:
let text = "My Text"
let index = 2
let charSequence = text.unicodeScalars.map{ Character($0) }
let char = charSequence[index]
这是在常数时间内在指定索引处获取char的方法。
下面的示例不是在常数时间内运行,而是需要线性时间。所以如果你有很多搜索字符串索引使用上述方法。
let char = text[text.startIndex.advancedBy(index)]
顺便说一句,有几个函数可以直接应用于String的字符链表示,像这样:
var string = "Hello, playground"
let firstCharacter = string.characters.first // returns "H"
let lastCharacter = string.characters.last // returns "d"
结果类型为Character,但可以将其转换为String。
或:
let reversedString = String(string.characters.reverse())
// returns "dnuorgyalp ,olleH"
:-)
我是斯威夫特4号
let myString = "LOVE"
self.textField1.text = String(Array(myString)[0])
self.textField2.text = String(Array(myString)[1])
self.textField3.text = String(Array(myString)[2])
self.textField4.text = String(Array(myString)[3])