Constant

A class that represents immutable data.

Constant<T> objects contain inner copy of original model of class T and provide read-only access to fields.

Usage

For class

class TreeNode
{
    parent: TreeNode;
    value: string;
}

Lets create some data structure:

let root = new TreeNode();
root.value = "root";

let child = new TreeNode();
child.parent = root;
child.value = "child";

Probably it should be stored in some immutable store (like Redux one :wink:).

To provide new state with a garant of lack of mutation on original model we use Constant<TreeNode>:

let childConstant = new Constant(child);
...

console.log(childConstant); // is Constant<TreeNode> for child

let childValue = childConstant.get(c => c.value);
console.log(childValue); // "child"

let rootConstant = childConstant.get(c => c.root);
let rootValue = rootConstant.get(c => c.value);
console.log(rootValue); // "root"