let string = String("");
一、从某个位置开始截取：
public func substring(from index: Int) -> String {
if (self.count > index) {
let startIndex = self.index(self.startIndex, offsetBy: index);
let subString = self[startIndex..<self.endIndex];
return String(subString);
} else {
return "";
}
}
二、从零开始截取到某个位置：
public func substring(to index: Int) -> String {
if (self.count > index) {
let endindex = self.index(self.startIndex, offsetBy: index);
let subString = self[self.startIndex..<endindex];
return String(subString);
} else {
return self;
}
}
三、某个范围内截取
public func subString(rang rangs:NSRange) -> String{
var string = String();
if (rangs.location >= 0) && (self.count > (rangs.location+rangs.length)){
let startIndex = self.index(self.startIndex, offsetBy: rangs.location);
let endindex = self.index(self.startIndex, offsetBy: (rangs.location+rangs.length));
let subString = self[startIndex..<endindex];
string = String(subString);
}
return string;
}