Classes

ABJAD is an object-oriented language, that means you can define your own types!

Classes simply represents a custom type, where you defined some properties that a variable with this type has, as well as what are the methods that this type can access.

Syntax

Defining a Class

The syntax for defining a class in ABJAD is as the following:

1. The keyword صنف
2. The name of the class
3. An opening brace {
4. A set of declarations (variables, constants, functions, and constructors)
5. A closing brace }

Example

The following example defined a class of name إنسان which has:

• two variables: a string اسم and a number عمر
• a setter method to update the value of each variable

صنف إنسان {

  متغير مقطع اسم؛
  متغير رقم عمر؛
  
  دالة تعديل_الاسم(مقطع اسم_): لاشيء {
    اسم = اسم_؛
  }
  
  دالة تعديل_العمر(رقم عمر_): لاشيء {
    عمر = عمر_؛
  }

}

To define a variable of type انسان, you can do the following:

متغير انسان محمد = انشئ انسان()؛
محمد.تعديل_الاسم("محمد")؛
محمد.تعديل_العمر(22)؛
أكتب("الاسم: " + محمد.اسم + "، العمر: " + محمد.عمر)؛

As you can see, now we have a custom type called انسان and just as the above example, I can define variables of this type.

Once I do so, I can access all the declared variables and methods, that were declared in the class, from within the variable itself using the dot .

Defining a Constructor

To create an instance of a defined class, you need to define a constructor inside the class' declaration. A constructor is a special kind of function that is responsible of setting the state of the instance created. If no parameterless constructor is defined, the class can be instantiated by calling on a default one that does nothing (similar to the example above).

The syntax of defining a constructor is:

1. the keyword منشئ
2. open bracket (
3. arbitrary number of parameters (just like function declarations)
4. close bracket )
5. open brace {
6. some code
7. close brace }

Example

An example of a constructor added to the class defined above:

صنف إنسان {

  متغير مقطع اسم؛
  متغير رقم عمر؛
  
  منشئ(مقطع اسم_، رقم عمر_) {
    اسم = اسم_؛
    عمر = عمر_؛
  }

}

As you can see, with constructors we can define the values of the variables directly when instantiating a variable of the class, with no need to use setters for that.

Now to define a variable of type انسان, you can do this:

متغير انسان محمد = انشئ انسان("محمد"، 22)؛
أكتب("الاسم: " + محمد.اسم + "، العمر: " + محمد.عمر)؛

Multiple Constructors

You can declare more than one constructors for the same class as long as they don't have the same order of parameters.

Example

صنف إنسان {

  متغير مقطع اسم؛
  متغير رقم عمر؛
  
  منشئ(مقطع اسم_، رقم عمر_) {
    اسم = اسم_؛
    عمر = عمر_؛
  }
  
منشئ(رقم عمر_) {  
    اسم = "بلا اسم"؛
    عمر = عمر_؛
  }

}

متغير انسان محمد = انشئ انسان("محمد"، 22)؛
أكتب("الاسم: " + محمد.اسم + "، العمر: " + محمد.عمر)؛

متغير انسان أحمد = انشئ انسان(31)؛
أكتب("الاسم: " + أحمد.اسم + "، العمر: " + أحمد.عمر)؛

Instantiating a Class

The syntax for instantiating a class in ABJAD is as the following:

1. The keyword انشئ
2. The name of the class
3. An opening parenthesis (
4. The parameters that the constructor takes, seperated by commas
5. A closing parenthesis )
6. A semicolon ؛

Accessing a Class's functions

To access the functions of a class's object, you type the name of the object, followed by a dot, then the name of the function you want to access, giving it the needed parameters.

Getters and Setters

To get the value of a field, it is recommended to use a member function rather than accessing it directly.

There are two convensional functions in this manner:

• Getters: are functions that simply return the value of the field.
• Setters: are functions that modify the value of the field.