一、Swift字符串操作，常用的一些方法，获取字符串长度，字符串首字母大写，字符串全部大写等
<pre>
/// 一些常用string方法
func otherStringOperator() {
var originStr = "Hello swift a,w 'ss @#'skk.kk"
print(originStr.characters.count)
print(originStr.contains("origin"))
print(originStr.uppercased())
print(originStr.capitalized) // 单词首字母大写,空格 , .为首字母大写依据
print(originStr)
}
</pre>
二、截取字符串
swift截取子串主要有三个方法，到某个位置结束、从某个位置开始，或者指定开始和结束的位置，其中需要用到String.Index。这个index代表一个位置，一般是从某个位置偏移多少。如果要获取首个和最后一个位置，可以使用endIndex和startIndex
<pre>
// 截取字符串
func doSubString() {
let originStr = "this is an origin string,I want get some substring form there"
print("到某个位置结束或者从某个位置开始")
let start1 = originStr.index(originStr.startIndex, offsetBy: 5)
let index1 = originStr.index(start1, offsetBy: 4)
let sub1 = originStr.substring(to: index1) // 从开始到某个位置
let sub11 = originStr.substring(from: index1) // 从某个位置到结束
print(sub1)
print(sub11)
print("字符串分割")
let sub2 = originStr.components(separatedBy: ",")
for item in sub2 {
print(item)
}
if let index3 = originStr.index(originStr.startIndex, offsetBy: 4, limitedBy: originStr.endIndex) {
let sub3 = originStr.substring(to: index3)
print(sub3)
}
print("截取指定位置、指定长度的字符串")
let start = originStr.index(originStr.startIndex, offsetBy: 11)
// let end = originStr.index(originStr.startIndex, offsetBy: 23)
let end = originStr.index(start, offsetBy: 13) // 从开始位置、偏移量，获取的是一个下标
if start <= end {
let range = Range(uncheckedBounds: (start, end))
let sub4 = originStr.substring(with: range)
print(sub4)
} else {
print("start must <= end")
}
}
</pre>
三、字符串替换
前面的index和Range如果弄清楚的话，字符串替换会比较容易理解。字符串替换可以自己指定一个Range，然后替换成对应的字符串，也可以先在原来的字符串中查找一个range，然后进行替换
<pre>
/// 字符串替换
func doStringReplace() {
var originStr = "this is a origin string,I want get some substring form there"
if let range = originStr.range(of: ",") {
let str1 = originStr.replacingCharacters(in: range, with: ", ")
print(str1)
let str2 = originStr.replacingOccurrences(of: " ", with: "-")
print(str2)
let str3 = originStr.remove(at: range.upperBound)
print(str3)
originStr.removeSubrange(range)
}
print(originStr)
}
</pre>
四、附上一个字符串的扩展
可以根据开始位置，结束位置，或者开始位置，指定长度获取子串，有些类似java中获取字符串的方法。有需要的话，还可以扩展传负数的情况，从字符串的末尾截取，但是使用上面的两个方法可以进行变通。
<pre>
extension String {
/// 从指定位置截取指定长度字符串
func substring(from start: Int, length: Int) -> String? {
if start > self.characters.count {
print("起始位置过长")
return nil
}
if start + length > self.characters.count {
print("截取位置错误")
return nil
}
if start < 0 || length < 0 {
return nil
}
if length == 0 {
return nil
}
let startIndex = self.index(self.startIndex, offsetBy: start)
let endIndex = self.index(startIndex, offsetBy: length)
return self.substring(with: Range(uncheckedBounds: (startIndex, endIndex)))
}
/// 指定开始位置和结束位置
func substring(from start: Int = 0, end: Int = 0) -> String? {
let length = end - start
return self.substring(from: start, length: length)
}
}
func testSubString() {
let origin = "hello world!"
print(origin.characters.count)
print(origin.endIndex)
if let sub = origin.substring(from: 0, length: 10) {
print(sub)
}
guard let sub = origin.substring(from: origin.characters.count - 6, end: origin.characters.count) else {
print("截取出错")
return
}
print(sub)
}
testSubString()
</pre>
