是时候承认失败了……
在Objective-C中，我可以使用如下内容:
NSString* str = @"abcdefghi";
[str rangeOfString:@"c"].location; // 2
在Swift中，我看到了类似的东西:
var str = "abcdefghi"
str.rangeOfString("c").startIndex
.．.但这只是给了我一个字符串。索引，我可以使用它下标回原始字符串，但不能从中提取位置。
FWIW，字符串。Index有一个名为_position的私有ivar，其中有正确的值。我只是不明白怎么会暴露出来。
我知道我自己可以很容易地将其添加到String中。我更好奇在这个新的API中我缺少了什么。
当前回答
extension String {
// MARK: - sub String
func substringToIndex(index:Int) -> String {
return self.substringToIndex(advance(self.startIndex, index))
}
func substringFromIndex(index:Int) -> String {
return self.substringFromIndex(advance(self.startIndex, index))
}
func substringWithRange(range:Range<Int>) -> String {
let start = advance(self.startIndex, range.startIndex)
let end = advance(self.startIndex, range.endIndex)
return self.substringWithRange(start..<end)
}
subscript(index:Int) -> Character{
return self[advance(self.startIndex, index)]
}
subscript(range:Range<Int>) -> String {
let start = advance(self.startIndex, range.startIndex)
let end = advance(self.startIndex, range.endIndex)
return self[start..<end]
}
// MARK: - replace
func replaceCharactersInRange(range:Range<Int>, withString: String!) -> String {
var result:NSMutableString = NSMutableString(string: self)
result.replaceCharactersInRange(NSRange(range), withString: withString)
return result
}
}
其他回答
extension String {
// MARK: - sub String
func substringToIndex(index:Int) -> String {
return self.substringToIndex(advance(self.startIndex, index))
}
func substringFromIndex(index:Int) -> String {
return self.substringFromIndex(advance(self.startIndex, index))
}
func substringWithRange(range:Range<Int>) -> String {
let start = advance(self.startIndex, range.startIndex)
let end = advance(self.startIndex, range.endIndex)
return self.substringWithRange(start..<end)
}
subscript(index:Int) -> Character{
return self[advance(self.startIndex, index)]
}
subscript(range:Range<Int>) -> String {
let start = advance(self.startIndex, range.startIndex)
let end = advance(self.startIndex, range.endIndex)
return self[start..<end]
}
// MARK: - replace
func replaceCharactersInRange(range:Range<Int>, withString: String!) -> String {
var result:NSMutableString = NSMutableString(string: self)
result.replaceCharactersInRange(NSRange(range), withString: withString)
return result
}
}
如果你想知道一个字符作为int值在字符串中的位置，使用这个:
let loc = newString.range(of: ".").location
斯威夫特5
查找子字符串的索引
let str = "abcdecd"
if let range: Range<String.Index> = str.range(of: "cd") {
let index: Int = str.distance(from: str.startIndex, to: range.lowerBound)
print("index: ", index) //index: 2
}
else {
print("substring not found")
}
查找字符索引
let str = "abcdecd"
if let firstIndex = str.firstIndex(of: "c") {
let index: Int = str.distance(from: str.startIndex, to: firstIndex)
print("index: ", index) //index: 2
}
else {
print("symbol not found")
}
String是NSString的桥接类型，add
import Cocoa
到你的swift文件，并使用所有“旧”的方法。
下面是一个干净的String扩展，回答了这个问题:
斯威夫特3:
extension String {
var length:Int {
return self.characters.count
}
func indexOf(target: String) -> Int? {
let range = (self as NSString).range(of: target)
guard range.toRange() != nil else {
return nil
}
return range.location
}
func lastIndexOf(target: String) -> Int? {
let range = (self as NSString).range(of: target, options: NSString.CompareOptions.backwards)
guard range.toRange() != nil else {
return nil
}
return self.length - range.location - 1
}
func contains(s: String) -> Bool {
return (self.range(of: s) != nil) ? true : false
}
}
斯威夫特2.2:
extension String {
var length:Int {
return self.characters.count
}
func indexOf(target: String) -> Int? {
let range = (self as NSString).rangeOfString(target)
guard range.toRange() != nil else {
return nil
}
return range.location
}
func lastIndexOf(target: String) -> Int? {
let range = (self as NSString).rangeOfString(target, options: NSStringCompareOptions.BackwardsSearch)
guard range.toRange() != nil else {
return nil
}
return self.length - range.location - 1
}
func contains(s: String) -> Bool {
return (self.rangeOfString(s) != nil) ? true : false
}
}
