NSString类中提供了这样三个方法用于获取子字符串：

• substringFromIndex:
• substringWithRange:
• substringToIndex:

具体的使用见下面代码即可知道。

NSString *str = @"12345";// NSString *subString0 = [str substringFromIndex:-1];   //会放生越界错误NSString *subString1 = [str substringFromIndex:0];       //@"12345"NSString *subString2 = [str substringFromIndex:1];       //@"2345"NSString *subString3 = [str substringFromIndex:4];       //@"5"NSString *subString4 = [str substringFromIndex:5];       //@""// 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:0];         //@"“NSString *subString12 = [str substringToIndex:1];         //@"1”NSString *subString13 = [str substringToIndex:4];         //@"1234“NSString *subString14 = [str substringToIndex:5];         //@"12345”// NSString *subString15 = [str substringToIndex:6];     //会放生越界错误NSRange range1 = NSMakeRange(-1, 5);NSRange range2 = NSMakeRange(0, 6);NSRange range3 = NSMakeRange(0, 5);NSRange range4 = NSMakeRange(1, 4);NSRange range5 = NSMakeRange(0, 0);NSRange range6 = NSMakeRange(4, 1);//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”
复制代码