Add stateTransforms step

Author: goatslacker

docs/index.md

@@ -90,6 +90,10 @@ class MyStore {
 }
 ```
 
+#### stateTransforms
+
+This is an array of functions you can provide which will be executed every time `createStore` or `createUnsavedStore` is ran. It will iterate through the array applying each function to your store. This can be useful if you wish to perform any pre-processing or transformations to your store before it's created.
+
 #### setState
 
 > setState(currentState: object, nextState: object): object

src/alt/index.js

@@ -11,7 +11,11 @@ import * as Sym from './symbols/symbols'
 import * as StateFunctions from './utils/StateFunctions'
 import createStoreConfig from './utils/createStoreConfig'
 
-const { createStoreFromObject, createStoreFromClass } = StoreUtils
+const {
+  createStoreFromObject,
+  createStoreFromClass,
+  transformStore
+} = StoreUtils
 const {
   ACTION_HANDLER,
   ACTION_KEY,
@@ -36,6 +40,7 @@ class Alt {
     this.dispatcher = config.dispatcher || new Dispatcher()
     this.actions = {}
     this.stores = {}
+    this.storeTransforms = config.storeTransforms || []
     this[LAST_SNAPSHOT] = this[INIT_SNAPSHOT] = '{}'
   }
 
@@ -46,15 +51,17 @@ class Alt {
   createUnsavedStore(StoreModel, ...args) {
     const key = StoreModel.displayName || ''
     createStoreConfig(this.config, StoreModel)
+    const Store = transformStore(this.storeTransforms, StoreModel)
 
-    return typeof StoreModel === 'object'
-      ? createStoreFromObject(this, StoreModel, key)
-      : createStoreFromClass(this, StoreModel, key, ...args)
+    return typeof Store === 'object'
+      ? createStoreFromObject(this, Store, key)
+      : createStoreFromClass(this, Store, key, ...args)
   }
 
   createStore(StoreModel, iden, ...args) {
     let key = iden || StoreModel.displayName || StoreModel.name || ''
     createStoreConfig(this.config, StoreModel)
+    const Store = transformStore(this.storeTransforms, StoreModel)
 
     if (this.stores[key] || !key) {
       if (this.stores[key]) {
@@ -69,9 +76,9 @@ class Alt {
       key = uid(this.stores, key)
     }
 
-    const storeInstance = typeof StoreModel === 'object'
-      ? createStoreFromObject(this, StoreModel, key)
-      : createStoreFromClass(this, StoreModel, key, ...args)
+    const storeInstance = typeof Store === 'object'
+      ? createStoreFromObject(this, Store, key)
+      : createStoreFromClass(this, Store, key, ...args)
 
     this.stores[key] = storeInstance
     saveInitialSnapshot(this, key)

src/alt/utils/StoreUtils.js

@@ -32,6 +32,10 @@ function doSetState(store, storeInstance, state) {
   }
 }
 
+export function transformStore(transforms, StoreModel) {
+  return transforms.reduce((Store, transform) => transform(Store), StoreModel)
+}
+
 export function createStoreFromObject(alt, StoreModel, key) {
   let storeInstance
 

test/alt-config-object.js

@@ -63,5 +63,10 @@ export default {
 
     assert.deepEqual(snapshot, {MyStore: {wrapper: {number: 2, letter: 'a'}}})
     assert.deepEqual(alt.getStore('MyStore').getState(), {number: 2, letter: 'a'})
-  }
+  },
+
+  'custom transforms'() {
+    const alt = new Alt({ stateTransforms: [] })
+    assert.isArray(alt.stateTransforms)
+  },
 }

test/store-transforms-test.js

@@ -0,0 +1,37 @@
+import { assert } from 'chai'
+import Alt from '../dist/alt-with-runtime'
+
+const alt = new Alt()
+
+alt.storeTransforms.push(function (Store) {
+  Store.test = 'hello'
+  return Store
+})
+
+class Store {
+  constructor() {
+    this.x = 0
+  }
+}
+
+class Store2 {
+  constructor() {
+    this.y = 0
+  }
+}
+
+export default {
+  'store transforms': {
+    'when creating stores alt goes through its series of transforms'() {
+      const store = alt.createStore(Store)
+      assert(alt.storeTransforms.length === 1)
+      assert.isDefined(store.test)
+      assert(store.test === 'hello', 'store that adds hello to instance transform')
+    },
+
+    'unsaved stores get the same treatment'() {
+      const store2 = alt.createUnsavedStore(Store)
+      assert.isDefined(store2.test)
+    },
+  },
+}