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Freeze

Freeze is an immutable data structure library for Roblox Luau.

Immutable data structures are imperative for use with popular libraries such as React and Rodux. To learn more about why immutability is important, check out our How does immutability help? page.

Freeze is fully1 typed and currently used in several duckarmor projects.

Use Freeze to create immutable data structures like so:

local map1 = { a = 1, b = 2, c = 3 }
local map2 = Freeze.Dictionary.set(map1, "b", 50)

print(map1.b, "vs", map2.b)
-- 2 vs 50

Freeze will optimize return calls in such that it will return the original list or dictionary if no changes were made:

local map1 = { a = 1 }
local map2 = Freeze.Dictionary.set(map1, "a", 1)

print(map1 == map2)
-- true; because no changes were made

True to it's name, Freeze will return calls of new values wrapped in table.frozen. Return values that are not changed will not be table.frozen'd to preserve the caller's frozen status.

Nested Data Structures​

Freeze also has a few power tools at your disposal to allow for reading and operating on nested data structures. These include getIn, setIn, mergeIn, and updateIn, found on Dictionary.

Freeze's General Philosophy​

Freeze aims to

  • Be type safe. Types are represented in such that there are no false negative type errors.
  • Be runtime safe. Errors will not propagate unless you are passing invalid values that the Luau type checker would have caught.
  • Enforce immutability via table.frozen
  • Optimize return values if no changes were made within the operation by returning the original value.

Prior art​

Freeze takes inspiration from:

  1. To the best of Luau's and my own ability.↩