boxm
Turning properties into objects
Usage
; // get a reference to the firstName property; // get/set the property value;firstNameProperty.set"Jim"; // grab several references in one hit (destructuring);
Installation
npm install --save boxm
(Type declarations are included of course.)
Dependency-free
Although it is useful with React and MobX (and the name is a play on MobX, as well as box 'em), boxm
has no runtime package dependencies itself.
Purpose
This library provides a way to conveniently grab a "reference" to a mutable property, with static type safety for TypeScript users.
Properties are named features of objects and so to address one for reading/writing you need to know the object and the name of the property. This can lead to ugly bifurcation and the use of "stringly typed" interfaces.
It's better to make an object with a static get
/set
interface that encapsulates one property:
This can then be passed around as a first-class value. All that's needed is a succinct way to create such an object.
Fun, Exciting Use-case
In MobX you typically have an object holding the current state of the UI (or a piece of the UI):
And in React you can create modular components. These might be as elemental as a single text input field:
With such a component you can describe the UI:
; return ;
This achieves simple two-way binding, via the box
function, with obvious clarity and static type-safety. If we'd just said person.lastName
we'd be passing the value, so the TextInput
component would not be able to modify the value, but by saying box(person).lastName
we're passing a wrapper that supports both get
and set
operations on the value of person.lastName
.
Advanced API
You can create a box
-like function from any function that can create a BoxValue
, by wrapping it with the boxer
higher order function:
;
So it accepts a "dynamic" means of boxing a single property, and returns a function that provides the same facility through the statically type-checked API of boxm
.
The function makeBoxedValue
, is suitable for passing directly to boxer
to duplicate the standard behaviour:
;
(The returned object has a prototype, which serves as a hint to MobX to handle it transparently.)
Combining these two pieces, we get the implementation of box
:
;
For example, this is how bidi-mobx defines its own MobX-optimal version of box
. It falls back to makeBoxedValue
if it can't do any better:
;
License
MIT