User Guide #19 - Ruby - variables

Ruby, ruby lesson, ruby уроки, user guide, variables, переменные, руководство пользователя

Ruby has three kinds of variables, one kind of constant and exactly two pseudo-variables. The variables and the constants have no type. While untyped variables have some drawbacks, they have many more advantages and fit well with ruby's quick and easy philosophy.

Variables must be declared in most languages in order to specify their type, modifiability (i.e., whether they are constants), and scope; since type is not an issue, and the rest is evident from the variable name as you are about to see, we do not need variable declarations in ruby.

The first character of an identifier categorizes it at a glance:

  • $ - global variable
  • @ - instance variable
  • [a-z] или _ - local variable
  • [A-Z] - constant

The only exceptions to the above are ruby's pseudo-variables: self , which always refers to the currently executing object, and nil , which is the meaningless value assigned to uninitialized variables. Both are named as if they are local variables, but self is a global variable maintained by the interpreter, and nil is really a constant. As these are the only two exceptions, they don't confuse things too much.

You man not assign values to self or nil . main , as a value of self , refers to the top-level object:

ruby> self
   main
ruby> nil
   nil
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Feb. 17, 2020, 2:41 p.m.
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Feb. 17, 2020, 3:22 a.m.
Evgenij Legotskoj

Добрый день. Это кастомный тег, помещается в файл, который находится в каталоге templatetags myapp/ templatetags/ myapp.py
B
Feb. 16, 2020, 1:36 p.m.
BahaMeirman

Добрый вечер! Монжно по подробней о теге get_companion? ссылка не работает.
Feb. 16, 2020, 9:35 a.m.
Evgenij Legotskoj

Добрый день. На GitHub исходники, можете посмотреть в официальном репозитории
B
Feb. 16, 2020, 9:29 a.m.
BahaMeirman

Здравстсвуйте Евгений, непонятно мне где эти исходники найти?
Now discuss on the forum
Feb. 22, 2020, 1:05 p.m.
BlinCT

Всем привет. Для моей приложухи требуется доступ к хедерам дял чтения данных, но к ним имеет доступ рут, без него чтение не происходит. Но как я слышал можно вроде через dbus или polki…
VZ
Feb. 21, 2020, 5:19 a.m.
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Здравствуйте! Пишу игру - 2D платформер в среде Qt. Имею не очень много опыта в разработке. Подскажите, как можно реализовать ситуацию, где QGraphicScene больше, чем QGraphicView и надо двигать …
Feb. 20, 2020, 7:12 a.m.
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Вот так похоже можно https://doc.qt.io/qt-5/qtpurchasing-index.html
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Feb. 20, 2020, 1:24 a.m.
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QSqlQuery query("SELECT CONCAT("#", LPAD(HEX(`t`.RGB), 6, 0)) FROM table AS t");query.exec(); while (query.next()) { QColor(query.value(0).toString()); }
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