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?

You probably should tag ruby first, and explain what those do. — Anubian Noob, May 26 '14 at 20:14
You may use `freeze` method. See http://rubylearning.com/satishtalim/mutable_and_immutable_objects.html — Dmitry Ginzburg, May 26 '14 at 20:20

score 7 · Accepted Answer · answered May 26 '14 at 20:23

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.

score 2 · Answer 2 · answered May 26 '14 at 20:23

2

If you want to create, for example, unmodifiable (immutable) list:

a = [ "a", "b", "c" ]
a.freeze

answered May 26 '14 at 20:23

Dmitry Ginzburg

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

2 Answers2