reselect-tree

reselect-tree
=============

Wrapper around reactjs's reselect
library for creating trees of selectors.

Designed to allow selectors to be organized into separate namespaces easily,
with the ability to identify dependencies between selectors in the tree.

Usage Example
=============

Install with:

``
npm install --save reselect-tree
`


Then define a file selectors.js:

`javascript
import { createSelectorTree, createLeaf } from "reselect-tree";

const selectors = require("./dist/reselect-tree.js");
const createSelectorTree = selectors.createSelectorTree;
const createLeaf = selectors.createLeaf;

const select = createSelectorTree({
shop: {
taxPercent: state => state.shop.taxPercent
},
cart: {
items: state => state.cart.items,

subtotal: createLeaf(
['./items'],

(items) => items.reduce((acc, item) => acc + item.value, 0)
),

tax: createLeaf(
['/shop/taxPercent', './subtotal'],

(taxPercent, subtotal) => subtotal * (taxPercent / 100)
),

total: createLeaf(
['./subtotal', './tax'], (subtotal, tax) => ({ total: subtotal + tax })
)
}
});


let exampleState = {
shop: {
taxPercent: 8,
},
cart: {
items: [
{ name: 'apple', value: 1.20 },
{ name: 'orange', value: 0.95 },
]
}
}

console.log(select.cart.subtotal(exampleState)) // 2.15
console.log(select.cart.tax(exampleState)) // 0.172
console.log(select.cart.total(exampleState)) // { total: 2.322 }
`

You can also select non-leaf nodes, for structured representations:

`javascript
console.log(select.cart(exampleState))
{ items:
[ { name: 'apple', value: 1.2 },
{ name: 'orange', value: 0.95 } ],
subtotal: 2.15,
tax: 0.172,
total: { total: 2.322 } }
`

Override Root Selectors
-----------------------

You can override the default aggregation behavior by defining a custom child
_. e.g.:

`javascript
const select = createSelectorTree({
shop: {
taxPercent: state => state.shop.taxPercent
},
cart: {
_: createLeaf(
['./items', './total'],

(items, total) => ({ items, total })
),

items: state => state.cart.items,

subtotal: createLeaf(
['./items'],

(items) => items.reduce((acc, item) => acc + item.value, 0)
),

tax: createLeaf(
['/shop/taxPercent', './subtotal'],

(taxPercent, subtotal) => subtotal * (taxPercent / 100)
),

total: createLeaf(
['./subtotal', './tax'], (subtotal, tax) => ({ total: subtotal + tax })
)
}
});
`

This changes how select.cart behaves, instead acting as select.cart._:

`javascript
console.log(select.cart(exampleState)); // { items:
// [ { name: 'apple', value: 1.2 },
// { name: 'orange', value: 0.95 } ],
// total: { total: 2.322 } }
console.log(select.cart._(exampleState)); // { items:
// [ { name: 'apple', value: 1.2 },
// { name: 'orange', value: 0.95 } ],
// total: { total: 2.322 } }
``