我习惯于在
JavaScript中执行此操作：
var domains = "abcde".substring(0,"abcde".indexOf("cd")) // Returns "ab"
Swift没有这个功能,怎么做类似的事情？
Xcode 8.3.1•Swift 3.1
extension String {
func index(of string: String,options: CompareOptions = .literal) -> Index? {
return range(of: string,options: options)?.lowerBound
}
func endIndex(of string: String,options: options)?.upperBound
}
func indexes(of string: String,options: CompareOptions = .literal) -> [Index] {
var result: [Index] = []
var start = startIndex
while let range = range(of: string,options: options,range: start..<endIndex) {
result.append(range.lowerBound)
start = range.upperBound
}
return result
}
func ranges(of string: String,options: CompareOptions = .literal) -> [Range<Index>] {
var result: [Range<Index>] = []
var start = startIndex
while let range = range(of: string,range: start..<endIndex) {
result.append(range)
start = range.upperBound
}
return result
}
}
用法：
let str = "Hello,playground,playground"
str.index(of: "play") // 7
str.endIndex(of: "play") // 11
str.indexes(of: "play") // [7,19,31]
str.ranges(of: "play") // [{lowerBound 7,upperBound 11},{lowerBound 19,upperBound 23},{lowerBound 31,upperBound 35}]
