I’ve been messing around with Objective-C and developing in OSX. So I was reading a tutoral using SQLite3 and the tutoral did something I’d never seen or thought of with the database object. He had the list object populate only the ids (index/primary key) of the objects. Then when you tried to access any of the properties on the object, it would use that id to fetch the rest of the object.

Because of my ventures into the waters of Objective-C I’ve started to take another look at C. Why you ask? This is because Objective-C is just a thin layer on top of C, which means that anything that is written in C is also written for Objective-C.

So do people still use C? I haven’t used it in over 7 years and it was standardized in 1989 (that’s a very long time in computer years). As far as my personal experience goes, no, no one uses it anymore. But is that really the case? According to TIOBE (http://www.tiobe.com) C is the second most popular programming language in the world (C++ is third, C# is seventh.) Apparently, I’ve been hanging out with the wrong crowd.

So everyone is using C, so a simple Google search should return all sorts of cool libraries for me to play with right? I’m interested in game development, so what game libraries/frameworks/engines can I use? (If you’re wondering why I’m looking for libraries in C instead of Objective-C then see here) So I checked out 18 different open source game engines/libraries/frameworks. Only 5 of them where written in C (and a few where pretty dated). Eight of the 18 engines where written in C++, 3 in C#, 1 in Python, and 1 in Java. Most of the professional game engines I looked into where C++ with one notable exception, the ID Tech engine (Quake games) which is C. All this means that about 28% of game engines are in C while 45% of them are written in C++. It defiantly looks like C++ has the home field advantage.

What about something like databases? SQLite is written in C (I’ll post more about it later). MySql is a mix of C and C++, PostgreSQL is C, and Oracle is C and assembly. Here it looks like C is king. I don’t know if this is due to historical reasons (doubtful in SQLites case) or if there is just something about C that tends its-self easer to database development.

While C is popular and a lot of software is still written in it, it seems to come down to what you want to accomplish. Game development has a strong tint of C++. Luckily, if you only care about developing for OS X you can have the best of all worlds. Xcode lets you mix C and C++ with Objective-C.

I’ve started to learn Objective-C, the programming language for Macs and the iPhone. So far I really like it. The philosophy and syntax around it are quite different from anything I’m used to. In most Object Oriented Languages, You have very strict classes with inheritance and methods; properties for accessing those classes. And in most OOLs (Object Oriented Languages) you have something called generics so that you don’t have to keep creating new classes because of a type difference. (Types are like numbers vs strings BTW.) If I have a list of integers (numbers) then I don’t have to make a second list just so I can have a list of strings. In fact a lot of time and effort goes into this sort of thing. (There is also the fragile base class problem.) This is where Objective-C really shines.

Objective-C is C with SmallTalk features added. The biggest difference is how object methods are called. In C# (or C++ or Java or whatever) if you want to call a method you use the ‘.’ dot operator (or ‘->’ arrow operator in C++.) For Example, pretend ‘Cat’ is an object with a single method of ‘Speak’. In C# you would write ‘Cat.Speak();’ to call the Speak method of the Cat object. In Objective-C however you don’t call methods directly. You pass messages to objects. So in our example we would write ‘[Cat Speak]‘ in Objective-C. On the surface this looks like a small syntax change. Instead of a ‘.’ operator you place the items in ‘[]‘ brackets with a space. But what these two items actually do is the key.

In C# the Cat method must have a Speak method or else it will throw an error. And that Speak method’s signature must match exactly. (signature is the Return Type and all the parameters [in order] on the method.) In Objective-C on the other hand, the Cat object doesn’t need to have a Speak method. If it doesn’t, the call will simply return false. No errors will be thrown. (Warnings will be thrown since we did specify a type.)

“But Chris!”, you say, “That’s one of the strengths of C#!” (I don’t know why you use so many exclamation marks, I can hear you, I promise.) And you’re right, type checking is a strong feature of those languages. You could tell Objective-C to throw errors in these situations. But let me explain why this is such a good thing.

If you’ve ever programmed a larger application, then you will be familiar with the concept of boxing and/or generics. (I’m going to stick with C# examples.) Now let’s say you write an application for a pet hospital. You need to keep a list of all the pets in the system. Let’s also assume each type of pet has it’s own class. (Cat, Dog, Snake, Hamster, Birds, Fish, pygmy goat, etc.) You have two choices: You could use boxing to add them all to an ArrayList of objects (because all classes inherit from object). Or you could use Generics to create a list for each type of Animal. Both of these methods are reasonable but have problems. They both require you to know the type of the object at compile time (or be able to get the type so you can cast it.) The reason is, not all of the animals will have the same methods. Not all of them can ‘Speak’ or ‘Fly’ so if you need to call those methods, you need to know the type at compile time or else an error will be thrown. Now there are creative ways to get around this problem. Which is why I said a lot of code and time is spent trying to get around this issue in the first paragraph.

But this really isn’t a problem in Objective-C. You can store all the animals in a single list, and not worry about if they implement ‘Speak’ or ‘Fly’. You can call the methods on ALL of the objects. Only the ones that actually implement the method will do something. All the time and energy to get around this problem in other languages is simply a non-issue in Objective-C. This isn’t Objective-C’s only strength, just one that I thought was most relevant to my daily programming.

There is one tremendous problem with Objective-C. The base classes (called Foundation) are Mac only. GNUStep tries to implement Foundation and some others on Windows and Linux but the downside is to great. Window users would have to install GNUStep (which isn’t an easy process and involves MinGW) in order to use anything in Objective-C. Until Foundation can either be statically built into the application, or a simple (like a DLL) way to include it is developed, I’m afraid Objective-C is going to stay Mac only. Not only that, but in limited use on the Mac (you can use C++ on the Mac).

Apple pushes Objective-C but that just isn’t enough in my opinion. Someone (preferably Apple) needs to make at least the core classes available for the three major operating systems (Windows, OSX, Linux). If there where to happen, then I think Objective-C could gain a lot of traction. Over time it could gain more support than C# or Java, or maybe even C++. But for now that is just my fantasy. I can use Objective-C for iPhone development and OSX development. That will have to be enough for now. I’ll just stick to C# for my windows development.

I switched over to Apple in 2003/2004 ish, and I’ve never really done any programming on it. Because of the iPhone, my intrest in apple development has peaked. So these last few days I’ve been looking into it and building some sample apps in XCode.

I’m intrested in building a Visual Novel of sorts. As a kid I loved choose your own adventure books and I’ve played a few VN that I liked. I’ve also played a bunch that I hated.

But being the writer & programmer that I am. I thought it could be fun to build my own.

There are a number of ways I could build this, the easyest being HTML and JavaScript (another AIR app). But I kinds want this to be on the iPhone (partly becuase if it successeds I could sell it).

So now I’m looking at how it can be done in objective-c and cocoa. To be honest I haven’t programmed in C (or C++) in over 7 years. Looking over samples rings some bells, but Cocoa is a new beast all together. Anyway, I think I’m going to try this objective-c programming.

I know this isn’t very zen of me. I could have something up and running in a matter of hours if I stuck with JavaScript or C#. I don’t even have a story or graphics yet. I just have a vage idea of a zombie survival story.

I really should write the story first, then worry about programming.

Still, I find myself here even when I know I shouldn’t.

I’ve been having problems completing this next step. I think I’ve been trying to solve two difficult problems at once. The Dynamic loading of the property, and the joining of the two tables.

So I’m taking a step back. Let’s solve the join first. How can I solve this problem with the code I already have?
Well I could just manually make the call to Tag in the User property. I would need to use the .Where() method to get what I want.
But, the .Where() method only looks at the objects table. I need to reference a joining table (tag_user to be exact.)

So, I need to be able to specify a joining table in the .Where() method, and then pull normally. I need to identify the table name, the matching columns, and then do the .Where() method normally.

Sounds good, I’ll get on this in the morning.

I changed some things around. I added a GetProperty and SetPropery because I didn’t like have to do a check all the time. I think it simplifies things and allows _properties to be private instead of protected.

I also created a GetColumns that gives the full name with an optional prefix for select statements. I created a GetTable to help out with this as well.

I which I could put this in the base class somehow, but we can simplify the code if the inherited class override the By and Where methods like so

        ///
        /// Get a single User By the property and value specified
        ///
        ///
        ///
        ///
        static public DBUser By(string property, object value)
        {
            return (DBUser)DBObject.By(property, value, typeof(DBUser), DBUser._conn);
        }

        ///
        /// Returns DBList where all the DBUsers have a matching property
        ///
        ///
        ///
        ///
        ///
        static public DBList Where(string property, string evaluator, object value)
        {
            return DBObject.Where(property, evaluator, value, typeof(DBUser), DBUser._conn);
        }

Then we can make simple calls like:

DBUser u3 = DBUser.By("firstname", "chris");
//and
DBList users1 = DBUser.Where("id", "<=", 1313);

Well I guess the next thing to do is to allow an object to relate to another object. For work I use tags for objects (as I discussed earlier) so that’s going to be my starting point.

So I have two objects. User and Tag.

A single User record can have an unlimited number of tags.
A single tag record can have only one user. But a Tag object can have an unlimited number of users.

So we have a many to many relationship, with a table joining them. The table already exists (tag_user) so I need to specify that.

When I get a user, it should get all of his tags as well, like wise when getting a tag it should get all the users. except that might not always be a good idea. What if I have 10,000 users with the tag ‘Public’ I might want to get that tag without getting all the users who have that tag. alsoIf i’m getting a list of users and they all have the ‘Public’ tag, it shouldn’t the tag shouldn’t pull that list of 10,000 for each user in my list. It should only pull it once, and thats only if I ever request it.

So I need to do some lazy loading. Say it only gets the related object if it’s requested. So if I get a list of users, it’ll just fill out that list. If I access the tags on one of the users, then it’ll go and fetch his tags.

So first things first:

Create Many to Many relationship, if you access the related object, then it goes and gets it.

Ok it works. I also created a checker for the opertators so we don’t get invalid/malicious code.

 ///
        /// Returns a DBList of objects that match the Where
        ///
        ///
Property to Match        ///
"=", "<", ">", "LIKE"        ///
Value to Match        ///
Type of the object to get (Must inherent from DBOBject)        ///
Connection String to use        ///
        static protected DBList Where(string property, string evaluator, object value, Type who_type, string connection)
        {
            DBList list = new DBList();

            //Find the Column Name and check that we have everything, if fail return the blank list
            string column_name = DBObject.GetColumn(property, who_type);
            if (column_name == string.Empty || evaluator == string.Empty || value == null) { return list; }
            //Check the evaluator, If fail, Return a blank list
            evaluator = DBObject.CheckEvaluator(evaluator);
            if (evaluator == string.Empty) { return list; }

            //Create the WHERE
            string query = DBObject.SelectQuery(who_type) + " WHERE " + column_name + " " + evaluator + "?value";

            using (MySqlConnection conn = new MySqlConnection(connection))
            {
                MySqlCommand cmd = new MySqlCommand(query, conn);
                cmd.Parameters.AddWithValue("?value", value);

                try
                {
                    conn.Open();
                    MySqlDataReader reader = cmd.ExecuteReader();

                    while (reader.Read())
                    {
                        DBObject obj = (DBObject)DBObject.FromReader(reader, who_type);
                        list.Add( obj );
                    }

                    conn.Close();
                }
                catch (Exception ex)
                {
                    Console.WriteLine("nnERROR:n" + ex.Message);
                }
            }

            //No matter what happens, always return a valid list
            return list;
        }

///
        /// Accepted Evaluators: '<', '<=', '>', '>=', '=', '!=', 'LIKE', 'REGEXP', 'IS NOT'
        ///
        ///
        ///
        static protected string CheckEvaluator(string evaluator)
        {
            //Lower and trim
            evaluator = evaluator.ToLower().Trim();

            switch (evaluator)
            {
                case "<":
                    return evaluator;
                    break;
                case "<=":
                    return evaluator;
                    break;
                case ">":
                    return evaluator;
                    break;
                case ">=":
                    return evaluator;
                    break;
                case "=":
                    return evaluator;
                    break;
                case "!=":
                    return evaluator;
                    break;
                case "like":
                    return evaluator;
                    break;
                case "regexp":
                    return evaluator;
                    break;
                case "is not":
                    return evaluator;
                    break;
                default:
                    return string.Empty;
            }
        }

And an example:

//Now lets try to get a list of users
            Console.WriteLine("nnTrying the Where Methiod");
            DBList users1 = DBObject.Where("id", "<=", 1313, typeof(DBUser), Utility.connMy);
            foreach (DBUser u4 in users1)
            {
                Console.WriteLine(u4.ID + " : " + u4.FullName);
            }

I have two thoughts of what the next step should be. The first is the ability to return a collection of objects (maybe LINQ computable, but I’m not worried about that right now.) The other is that the object should be able to fetch it’s own tags.

In my system, each object has tags associated with it. This allows objects to ‘subscribe’ to other objects. For example, we have a user object and a task object. The user can use tags to subscribe to a task (or many tasks). Many users can subscribe to a same task using this method. The tasks also have an optional prefix. This prefix can say things like; who owns the task, who can modify it, who can complete it, etc. (Just having the tag means you’ve subscribed and can thus view it.)
So when I get the object it really needs to go and fetch all if it’s tags as well.

Because objects rarely have only a single tag, I should probably start with the collections. I’m going to call them lists from now on. These lists must inherit from CollectionBase class in order keep compatibility.

So I think what I want, is a DBList : CollectionBase object that can be used as the return value for static methods.

So I could do something like