79d9012432
* fix(curriculum): tests quotes * fix(curriculum): fill seed-teardown * fix(curriculum): fix tests and remove unneeded seed-teardown
85 lines
4.0 KiB
Markdown
85 lines
4.0 KiB
Markdown
---
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id: 5a24c314108439a4d4036146
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title: Map Dispatch to Props
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challengeType: 6
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isRequired: false
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---
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## Description
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<section id='description'>
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The <code>mapDispatchToProps()</code> function is used to provide specific action creators to your React components so they can dispatch actions against the Redux store. It's similar in structure to the <code>mapStateToProps()</code> function you wrote in the last challenge. It returns an object that maps dispatch actions to property names, which become component <code>props</code>. However, instead of returning a piece of <code>state</code>, each property returns a function that calls <code>dispatch</code> with an action creator and any relevant action data. You have access to this <code>dispatch</code> because it's passed in to <code>mapDispatchToProps()</code> as a parameter when you define the function, just like you passed <code>state</code> to <code>mapStateToProps()</code>. Behind the scenes, React Redux is using Redux's <code>store.dispatch()</code> to conduct these dispatches with <code>mapDispatchToProps()</code>. This is similar to how it uses <code>store.subscribe()</code> for components that are mapped to <code>state</code>.
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For example, you have a <code>loginUser()</code> action creator that takes a <code>username</code> as an action payload. The object returned from <code>mapDispatchToProps()</code> for this action creator would look something like:
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<blockquote>{<br> submitLoginUser: function(username) {<br> dispatch(loginUser(username));<br> }<br>}</blockquote>
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</section>
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## Instructions
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<section id='instructions'>
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The code editor provides an action creator called <code>addMessage()</code>. Write the function <code>mapDispatchToProps()</code> that takes <code>dispatch</code> as an argument, then returns an object. The object should have a property <code>submitNewMessage</code> set to the dispatch function, which takes a parameter for the new message to add when it dispatches <code>addMessage()</code>.
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</section>
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## Tests
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<section id='tests'>
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```yml
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tests:
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- text: <code>addMessage</code> should return an object with keys <code>type</code> and <code>message</code>.
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testString: assert((function() { const addMessageTest = addMessage(); return ( addMessageTest.hasOwnProperty('type') && addMessageTest.hasOwnProperty('message')); })(), '<code>addMessage</code> should return an object with keys <code>type</code> and <code>message</code>.');
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- text: <code>mapDispatchToProps</code> should be a function.
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testString: assert(typeof mapDispatchToProps === 'function', '<code>mapDispatchToProps</code> should be a function.');
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- text: <code>mapDispatchToProps</code> should return an object.
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testString: assert(typeof mapDispatchToProps() === 'object', '<code>mapDispatchToProps</code> should return an object.');
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- text: Dispatching <code>addMessage</code> with <code>submitNewMessage</code> from <code>mapDispatchToProps</code> should return a message to the dispatch function.
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testString: assert((function() { let testAction; const dispatch = (fn) => { testAction = fn; }; let dispatchFn = mapDispatchToProps(dispatch); dispatchFn.submitNewMessage('__TEST__MESSAGE__'); return (testAction.type === 'ADD' && testAction.message === '__TEST__MESSAGE__'); })(), 'Dispatching <code>addMessage</code> with <code>submitNewMessage</code> from <code>mapDispatchToProps</code> should return a message to the dispatch function.');
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```
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</section>
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## Challenge Seed
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<section id='challengeSeed'>
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<div id='jsx-seed'>
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```jsx
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const addMessage = (message) => {
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return {
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type: 'ADD',
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message: message
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}
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};
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// change code below this line
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```
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</div>
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</section>
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## Solution
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<section id='solution'>
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```js
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const addMessage = (message) => {
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return {
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type: 'ADD',
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message: message
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}
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};
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// change code below this line
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const mapDispatchToProps = (dispatch) => {
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return {
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submitNewMessage: function(message) {
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dispatch(addMessage(message));
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}
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}
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};
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```
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</section>
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