Ruby equivalent of Java's Collections.unmodifiableList and Collections.unmodifiableMap

Question

Is there a equivalent in the Ruby standard API for Java's `Collections.unmodifiableList` and `Collections.unmodifiableMap`?

Accepted Answer

Use `freeze` API:

Prevents further modifications to obj. A RuntimeError will be raised if modification is attempted. There is no way to unfreeze a frozen object. See also Object#frozen?.

This method returns self.

```
a = [ "a", "b", "c" ]
a.freeze
a << "z"
```

produces:

```
prog.rb:3:in `<<': can't modify frozen array (RuntimeError)
 from prog.rb:3
```

You can also use the hamster gem for other immutable data structures.

Ruby equivalent of Java's Collections.unmodifiableList and Collections.unmodifiableMap

Solution

Problem