Add Observer render and inject sugar #387

README.md

@@ -83,8 +83,6 @@ The rendering in the function will be tracked and automatically re-rendered when
 This can come in handy when needing to pass render function to external components (for example the React Native listview), or if you
 dislike the `observer` decorator / function.
 
-Example:
-
 ```javascript
 class App extends React.Component {
   render() {
@@ -105,6 +103,56 @@ React.render(<App person={person} />, document.body)
 person.name = "Mike" // will cause the Observer region to re-render
 ```
 
+In case you are a fan of render props, you can use that instead of children. Be advised, that you cannot use both approaches at once, children have a precedence.
+
+Here goes example showing render prop only
+
+```javascript
+class App extends React.Component {
+  render() {
+     return (
+         <div>
+            {this.props.person.name}
+            <Observer
+              render={(props) => <div>{props.person.name}</div>}
+            />
+        </div>
+     )
+  }
+}
+
+const person = observable({ name: "John" })
+
+React.render(<App person={person} />, document.body)
+person.name = "Mike" // will cause the Observer region to re-render
+```
+
+Observer can also inject the stores simply by passing a selector function.
+
+Example with inject
+
+```javascript
+
+const NameDisplayer = ({ name }) => <h1>{name}</h1>
+
+const user = mobx.observable({
+    name: "Noa"
+})
+
+const UserNameDisplayer = ()=>(
+    <Observer
+        inject={(stores)=>({user:stores.user})}
+        render={props => (<NameDisplayer name={props.user.name}/>)}
+    />
+)
+
+const App = () => (
+    <Provider userStore={user}>
+        <UserNameDisplayer />
+    </Provider>
+)
+```
+
 ### Global error handler with `onError`
 
 If a component throws an error, this logs to the console but does not 'crash' the app, so it might go unnoticed.
@@ -438,3 +486,5 @@ Data will have one of the following formats:
 
 WeakMap. Its `get` function returns the associated reactive component of the given node. The node needs to be precisely the root node of the component.
 This map is only available after invoking `trackComponents`.
+
+

src/index.d.ts

@@ -65,7 +65,7 @@ export function onError(cb: (error: Error) => void): () => void
 
 export class Provider extends React.Component<any, {}> {}
 
-export class Observer extends React.Component<{ children?: () => React.ReactNode }, {}> {}
+export class Observer extends React.Component<{ children?: () => React.ReactNode, render?: () => React.ReactNode, inject?: IStoresToProps |  string[] }, {}> {}
 
 export function useStaticRendering(value: boolean): void
 

src/observer.js

@@ -1,5 +1,5 @@
 import { Atom, Reaction, extras } from "mobx"
-import { Component } from "react"
+import React, { Component } from "react"
 import { findDOMNode as baseFindDOMNode } from "react-dom"
 import EventEmitter from "./utils/EventEmitter"
 import inject from "./inject"
@@ -349,12 +349,41 @@ function mixinLifecycleEvents(target) {
 }
 
 // TODO: support injection somehow as well?
-export const Observer = observer(({ children }) => children())
+export const Observer = observer(({ children, inject: observerInject, render }) => {
+    const component = children || render
+    if (typeof component === "undefined") {
+        return null
+    }
+    if (!observerInject) {
+        return component()
+    }
+    const InjectComponent = inject(observerInject)(component)
+    return <InjectComponent />
+})
 
 Observer.displayName = "Observer"
 
 Observer.propTypes = {
+    render: (propValue, key, componentName, location, propFullName) => {
+        if (typeof propValue["children"] === "function") {
+            return
+        }
+        if (typeof propValue[key] !== "function")
+            return new Error(
+                "Invalid prop `" +
+                    propFullName +
+                    "` of type `" +
+                    typeof propValue[key] +
+                    "` supplied to" +
+                    " `" +
+                    componentName +
+                    "`, expected `function`."
+            )
+    },
     children: (propValue, key, componentName, location, propFullName) => {
+        if (typeof propValue["render"] === "function") {
+            return
+        }
         if (typeof propValue[key] !== "function")
             return new Error(
                 "Invalid prop `" +

test/observer.test.js

@@ -4,8 +4,8 @@ import ReactDOM from "react-dom"
 import ReactDOMServer from "react-dom/server"
 import TestUtils from "react-dom/test-utils"
 import * as mobx from "mobx"
-import { observer, inject, onError, offError, useStaticRendering, Observer } from "../"
-import { createTestRoot, sleepHelper, asyncReactDOMRender } from "./index"
+import { observer, inject, onError, offError, useStaticRendering, Observer, Provider } from "../"
+import { createTestRoot, sleepHelper, asyncReactDOMRender, asyncRender } from "./"
 import ErrorCatcher from "./ErrorCatcher"
 
 /**
@@ -16,12 +16,6 @@ const testRoot = createTestRoot()
 
 const getDNode = (obj, prop) => obj.$mobx.values[prop]
 
-const asyncRender = (element, root) => {
-    return new Promise(resolve => {
-        ReactDOM.render(<element />)
-    })
-}
-
 /*
  use TestUtils.renderIntoDocument  will re-mounted the component  with with different props
  some misunderstanding will be cause？
@@ -209,7 +203,6 @@ describe("does not views alive when using static rendering", () => {
     })
 
     test("no re-rendering on static rendering", () => {
-        expect(renderCount).toBe(1)
         data.z = "hello"
         expect(renderCount).toBe(1)
         expect(TestUtils.findRenderedDOMComponentWithTag(element, "div").innerHTML).toBe("hi")
@@ -533,9 +526,10 @@ describe("it rerenders correctly if some props are non-observables - 2", () => {
     }
 
     mobx.reaction(() => odata.x, v => console.log(v))
-
-    beforeAll(async () => {
+    
+    beforeAll(async done => {
         await asyncReactDOMRender(<Parent odata={odata} />, testRoot)
+        done()
     })
 
     test("init renderCount === 1", () => {
@@ -757,3 +751,60 @@ test.skip("195 - should throw if trying to overwrite lifecycle methods", () => {
         /Cannot assign to read only property 'componentWillMount'/
     )
 })
+
+describe("use Observer inject and render sugar should work  ", () => {
+    test("use render without inject should be correct", async () => {
+        const Comp = () => (
+            <div>
+                <Observer render={props => <span>{123}</span>} />
+            </div>
+        )
+        await asyncReactDOMRender(<Comp />, testRoot)
+        expect(testRoot.querySelector("span").innerHTML).toBe("123")
+    })
+
+    test("use children without inject should be correct", async () => {
+        const Comp = () => (
+            <div>
+                <Observer>{props => <span>{123}</span>}</Observer>
+            </div>
+        )
+        await asyncReactDOMRender(<Comp />, testRoot)
+        expect(testRoot.querySelector("span").innerHTML).toBe("123")
+    })
+
+    test("use render with inject should be correct", async () => {
+        const Comp = () => (
+            <div>
+                <Observer
+                    inject={store => ({ h: store.h, w: store.w })}
+                    render={props => <span>{`${props.h} ${props.w}`}</span>}
+                />
+            </div>
+        )
+        const A = () => (
+            <Provider h="hello" w="world">
+                <Comp />
+            </Provider>
+        )
+        await asyncReactDOMRender(<A />, testRoot)
+        expect(testRoot.querySelector("span").innerHTML).toBe("hello world")
+    })
+
+    test("use children with inject should be correct", async () => {
+        const Comp = () => (
+            <div>
+                <Observer inject={store => ({ h: store.h, w: store.w })}>
+                    {props => <span>{`${props.h} ${props.w}`}</span>}
+                </Observer>
+            </div>
+        )
+        const A = () => (
+            <Provider h="hello" w="world">
+                <Comp />
+            </Provider>
+        )
+        await asyncReactDOMRender(<A />, testRoot)
+        expect(testRoot.querySelector("span").innerHTML).toBe("hello world")
+    })
+})

test/ts/compile-ts.tsx

@@ -191,6 +191,18 @@ class ObserverTest extends Component<any, any> {
 	}
 }
 
+class ObserverTest2 extends Component<any, any> {
+	render() {
+		return <Observer render={() => <div>test</div>} />;
+	}
+}
+
+class ObserverTest3 extends Component<any, any> {
+	render() {
+		return <Observer inject={["store"]} render={() => <div>test</div>} />;
+	}
+}
+
 @observer
 class ComponentWithoutPropsAndState extends Component<{}, {}> {
     componentDidUpdate() {