Ruby

Question

I'm not sure how this is valid code: ``` class Library def initialize(games) @games = games end def add_game(game) games << game end def games() @games end end games = ['WoW','SC2','D3'] lib = Library.new(games) puts lib.games lib.add_game('Titan') puts lib.games ``` This will print out: WoW SC2 D3 Titan I would think that it should print out WoW SC2 D3 The add_game method doesn't use the instance variable. Being new to Ruby, I don't understand how this works. Shouldn't it have to be: ``` def add_games(game) @games << game end ``` I'm reading this from a tutorial and I haven't been able to find anything on how << works specifically with instance variables. I thought '<<' was just overloaded when dealing with arrays to be 'append to the array'. Is this actually doing something w/ Singleton classes?

Accepted Answer

This code is a little confusing. The line:

```
games << game
```

is actually calling the method `games`, which returns `@games`. Then the `<<` method is called on that result. There's some syntactic sugar in the Ruby parser that turns the `<<` operator into a method call on the left operand, and the left operand is being evaluated before that happens.

Edit for more clarity:

The line could be written like this:

```
(games).<< game
```

or this:

```
(self.games).<< game
```

or:

```
(self.games) << game
```

all of which execute the `games` method.

Ruby << (double less than) with instance variables

Solution

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