Question: I'm still pretty green when it comes to Ruby and am trying to figure out what this is doing:

```
 command_windows.each {|window| window.hidden ||= window.open?  } 

```

The `command_windows` variable appears to be an array of objects. If someone could explain to me what this line of code means, particularly what the ||= symbol is I would appreciate it.

Answer: 
`foo ||= "bar"` is the equivalent of doing `foo || foo = "bar"`.

As Mischa explained, it checks for a falsy value before assigning.

In your case, you could think of it as:

```
command_windows.each {|window| window.hidden || window.hidden = window.open?  }

```

which is another way of saying

```
command_windows.each {|window| window.hidden = window.open? unless window.hidden }

```
The `||=` operator is used to assign new value to variable. If something was assigned to it before it won't work. It is usually used in hashes, so you don't have to check, if something is already assigned.