Attempt at overloading arguments with factories

Author: tgriesser

src/components/connect.js

@@ -14,6 +14,13 @@ const defaultMergeProps = (stateProps, dispatchProps, parentProps) => ({
   ...dispatchProps
 })
 
+function isFunction(fn) {
+  return typeof fn === 'function'
+}
+function isFactory(fn) {
+  return isFunction(fn) && fn.length === 0 && isFunction(fn())
+}
+
 function getDisplayName(WrappedComponent) {
   return WrappedComponent.displayName || WrappedComponent.name || 'Component'
 }
@@ -23,56 +30,20 @@ let nextVersion = 0
 
 export default function connect(mapStateToProps, mapDispatchToProps, mergeProps, options = {}) {
   const shouldSubscribe = Boolean(mapStateToProps)
-  const finalMapStateToProps = mapStateToProps || defaultMapStateToProps
-  const finalMapDispatchToProps = isPlainObject(mapDispatchToProps) ?
+  const mapState = mapStateToProps || defaultMapStateToProps
+  const mapDispatch = isPlainObject(mapDispatchToProps) ?
     wrapActionCreators(mapDispatchToProps) :
     mapDispatchToProps || defaultMapDispatchToProps
+
+  const mapStateFactory = isFactory(mapState) ? mapState : (() => mapState)
+  const mapDispatchFactory = isFactory(mapDispatch) ? mapDispatch : (() => mapDispatch)
+
   const finalMergeProps = mergeProps || defaultMergeProps
-  const doStatePropsDependOnOwnProps = finalMapStateToProps.length !== 1
-  const doDispatchPropsDependOnOwnProps = finalMapDispatchToProps.length !== 1
   const { pure = true, withRef = false } = options
 
   // Helps track hot reloading.
   const version = nextVersion++
 
-  function computeStateProps(store, props) {
-    const state = store.getState()
-    const stateProps = doStatePropsDependOnOwnProps ?
-      finalMapStateToProps(state, props) :
-      finalMapStateToProps(state)
-
-    invariant(
-      isPlainObject(stateProps),
-      '`mapStateToProps` must return an object. Instead received %s.',
-      stateProps
-    )
-    return stateProps
-  }
-
-  function computeDispatchProps(store, props) {
-    const { dispatch } = store
-    const dispatchProps = doDispatchPropsDependOnOwnProps ?
-      finalMapDispatchToProps(dispatch, props) :
-      finalMapDispatchToProps(dispatch)
-
-    invariant(
-      isPlainObject(dispatchProps),
-      '`mapDispatchToProps` must return an object. Instead received %s.',
-      dispatchProps
-    )
-    return dispatchProps
-  }
-
-  function computeMergedProps(stateProps, dispatchProps, parentProps) {
-    const mergedProps = finalMergeProps(stateProps, dispatchProps, parentProps)
-    invariant(
-      isPlainObject(mergedProps),
-      '`mergeProps` must return an object. Instead received %s.',
-      mergedProps
-    )
-    return mergedProps
-  }
-
   return function wrapWithConnect(WrappedComponent) {
     class Connect extends Component {
       shouldComponentUpdate() {
@@ -91,13 +62,59 @@ export default function connect(mapStateToProps, mapDispatchToProps, mergeProps,
           `or explicitly pass "store" as a prop to "${this.constructor.displayName}".`
         )
 
+        this.configure()
         const storeState = this.store.getState()
         this.state = { storeState }
         this.clearCache()
       }
 
+      configure() {
+        this.finalMapStateToProps = mapStateFactory()
+        this.finalMapDispatchToProps = mapDispatchFactory()
+        this.doStatePropsDependOnOwnProps = this.finalMapStateToProps.length !== 1
+        this.doDispatchPropsDependOnOwnProps = this.finalMapDispatchToProps.length !== 1
+      }
+
+      computeStateProps(store, props) {
+        const state = store.getState()
+        const stateProps = this.doStatePropsDependOnOwnProps ?
+          this.finalMapStateToProps(state, props) :
+          this.finalMapStateToProps(state)
+
+        invariant(
+          isPlainObject(stateProps),
+          '`mapStateToProps` must return an object. Instead received %s.',
+          stateProps
+        )
+        return stateProps
+      }
+
+      computeDispatchProps(store, props) {
+        const { dispatch } = store
+        const dispatchProps = this.doDispatchPropsDependOnOwnProps ?
+          this.finalMapDispatchToProps(dispatch, props) :
+          this.finalMapDispatchToProps(dispatch)
+
+        invariant(
+          isPlainObject(dispatchProps),
+          '`mapDispatchToProps` must return an object. Instead received %s.',
+          dispatchProps
+        )
+        return dispatchProps
+      }
+
+      computeMergedProps(stateProps, dispatchProps, parentProps) {
+        const mergedProps = finalMergeProps(stateProps, dispatchProps, parentProps)
+        invariant(
+          isPlainObject(mergedProps),
+          '`mergeProps` must return an object. Instead received %s.',
+          mergedProps
+        )
+        return mergedProps
+      }
+
       updateStatePropsIfNeeded() {
-        const nextStateProps = computeStateProps(this.store, this.props)
+        const nextStateProps = this.computeStateProps(this.store, this.props)
         if (this.stateProps && shallowEqual(nextStateProps, this.stateProps)) {
           return false
         }
@@ -107,7 +124,7 @@ export default function connect(mapStateToProps, mapDispatchToProps, mergeProps,
       }
 
       updateDispatchPropsIfNeeded() {
-        const nextDispatchProps = computeDispatchProps(this.store, this.props)
+        const nextDispatchProps = this.computeDispatchProps(this.store, this.props)
         if (this.dispatchProps && shallowEqual(nextDispatchProps, this.dispatchProps)) {
           return false
         }
@@ -117,15 +134,15 @@ export default function connect(mapStateToProps, mapDispatchToProps, mergeProps,
       }
 
       updateMergedProps() {
-        this.mergedProps = computeMergedProps(
+        this.mergedProps = this.computeMergedProps(
           this.stateProps,
           this.dispatchProps,
           this.props
         )
       }
 
       isSubscribed() {
-        return typeof this.unsubscribe === 'function'
+        return isFunction(this.unsubscribe)
       }
 
       trySubscribe() {
@@ -203,10 +220,10 @@ export default function connect(mapStateToProps, mapDispatchToProps, mergeProps,
         let shouldUpdateDispatchProps = true
         if (pure && renderedElement) {
           shouldUpdateStateProps = hasStoreStateChanged || (
-            haveOwnPropsChanged && doStatePropsDependOnOwnProps
+            haveOwnPropsChanged && this.doStatePropsDependOnOwnProps
           )
           shouldUpdateDispatchProps =
-            haveOwnPropsChanged && doDispatchPropsDependOnOwnProps
+            haveOwnPropsChanged && this.doDispatchPropsDependOnOwnProps
         }
 
         let haveStatePropsChanged = false
@@ -265,6 +282,7 @@ export default function connect(mapStateToProps, mapDispatchToProps, mergeProps,
 
         // We are hot reloading!
         this.version = version
+        this.configure()
         this.trySubscribe()
         this.clearCache()
       }