1，substringFromIndex
从索引0开发到到index的后面的字符
2，substringWithRange
取指定range里面的字符，左边为索引index，右边为截取的范围
3，substringToIndex
从索引0到给定的索引index
代码如下：
NSString *str = @"";
// NSString *subString0 = [str substringFromIndex:-1]; //会放生越界错误 NSString *subString1 = [str substringFromIndex:]; //@"12345" NSString *subString2 = [str substringFromIndex:]; //@"2345" NSString *subString3 = [str substringFromIndex:]; //@"5" NSString *subString4 = [str substringFromIndex:]; //@"" // NSString *subString5 = [str substringFromIndex:6]; //会放生越界错误
// NSString *subString10 = [str substringToIndex:-1]; //会放生越界错误 NSString *subString11 = [str substringToIndex:]; //@"“ NSString *subString12 = [str substringToIndex:]; //@"1” NSString *subString13 = [str substringToIndex:]; //@"1234“ NSString *subString14 = [str substringToIndex:]; //@"12345” // NSString *subString15 = [str substringToIndex:6]; //会放生越界错误
NSRange range1 = NSMakeRange(-, ); NSRange range2 = NSMakeRange(, ); NSRange range3 = NSMakeRange(, ); NSRange range4 = NSMakeRange(, ); NSRange range5 = NSMakeRange(, ); NSRange range6 = NSMakeRange(, );
//NSString *subString31 = [str substringWithRange:range1]; //会放生越界错误 //NSString *subString32 = [str substringWithRange:range2]; //会放生越界错误 NSString *subString33 = [str substringWithRange:range3]; //@"12345“ NSString *subString34 = [str substringWithRange:range4]; //@"2345” NSString *subString35 = [str substringWithRange:range5]; //@"” NSString *subString36 = [str substringWithRange:range6]; //@"5”