关于 nsstring 包含，插入问题

NSString * fileName = @"bbbbbaaaabbbb.jpg";

NSString * seachName = @"工";

NSRange range = [fileName rangeOfString:seachName];

if (range.location != NSNotFound)

{ //包含

NSLog(@"包含");

NSMutableString * temp_String = [[NSMutableString alloc] initWithString:fileName];

[temp_String insertString:@"_p" atIndex:fileName.length-4];

NSLog(@"resString:%@",temp_String);

}else{

//不包含

NSLog(@"不包含玩个鸟");

}