String和url的截取

    NSNumber *number=[NSNumber numberWithDouble:[Amount doubleValue]];
    NSString *base=[From stringValue];
    NSString *target=[To stringValue];
    NSString *URLString=[NSString
    stringWithFormat:@"http://www.google.com/ig/calculator?hl=en&q=%@%@%%3D%%3F%@",number,base,target];
    NSString *content=[NSString stringWithContentsOfURL:[NSURL URLWithString:URLString]
                       encoding:NSASCIIStringEncoding error:nil];
    if (content!=nil) {
    int begin=[content rangeOfString:@"rhs: \""].location+[content rangeOfString:@"rhs: \""].length;
    content=[content substringFromIndex:begin];
    content=[content substringToIndex:[content rangeOfString:@" "].location];
    [result setStringValue:[@"result:" stringByAppendingString:content]];
    }