Classes, Functions and Variables

Content

• Classes
• Functions
• Variables
• Features visibility

Classes

Class declaration:

class
    APPLICATION
end

Class constructor (add create keyword with feature name)

class
    APPLICATION
create
    method_name
feature
    method_name(param1: CLASS_NAME; param2: CLASS_NAME)
        do
            -- do something
        end
end

Functions

Command (function with no return value) declaration

feature
    -- some code
    command
        do
            -- do something
        end
end

Command with parameters

feature
    -- some code
    command_with_params(param1: INTEGER; param2: STRING)
        do
            -- do something
        end
end

Query (function with the return value)

feature
    -- some code
    query(param1: CLASS1; param2: CLASS2): RETURN_CLASS
        do
            -- do something
            Result := some_variable -- set return value of the function
        end
end

Parameters with the same type can be declared in more compact way

feature
    -- some code
    fucntion_with_params(param1, param2, param3: INTEGER; param4: STRING)
        do
            -- do something
        end
end

Variables

Variable declaration (non-reference types)

feature
    name: STRING

For reference types (STRING + all user-written classes) you must initialize variable in the constructor:

create
    init
feature
    name: STRING

    init
        do
            name := "Name"
        end

You mark variable is detachable, in this case it will accept Void value (And you do not need to initialize it)

feature
    name: detachable STRING

Setter for variable

feature
    name: STRING assign set_name

    set_name(new_name: STRING)
        do
            name := new_name
        end

Constant declaration

feature
    id: INTEGER = 0 -- after that, it cannot be changed

Local variables - using local keyword:

feature
    some_function(param: STRING)
        local
            local_var: STRING -- note, that you do not need to initialize local variables of reference type
        do
            local_var := param -- can be used only inside current function
        end

Features visibility

To make function/variable accessisble only for certain class(es) use {CLASS1} or {CLASS1, CLASS2}:

feature{A, B} -- in this case, name and some_action() will be only accessible inside parent class, A and B
    name: STRING

    some_action
        do
        end

feature{NONE} -- in this case, name and some_action() will be only accessible inside parent class
    name: STRING

    some_action
        do
        end

You can define different visibility scopes in one class:

class C
    feature{A, B} -- only accessible inside parent class, A and B
        name: STRING
    feature{A} -- only accessible inside parent class and A
        age: INTEGER
    feature{NONE} -- only accessible inside parent class
        age: INTEGER
end