React: way to avoid Refs to access Child component's state - reactjs

So I've read that we should try avoiding refs when accessing Child components
(React refs with components)
(https://facebook.github.io/react/docs/more-about-refs.html)
In my case, however, I couldn't think of a way to avoid this in my situation..
Scenario:
I have a MyForm parent component which contains a TagInput child component, which resembles Stackoveflow's "Tags" input field. As the user types an input+SPACE, a tag is added to TagInput's internal state. When the user submits the form, the selected tag list is posted to my server.
Implementation:
var MyForm = React.createClass({
submit: function() {
var selectedTags = this.refs.tagInput.state.selectedTags;
$.post(
SERVER_URL,
data: { tags: selectedTags }
);
},
render: function() {
return (
<form onSubmit={this.submit}>
<TagInput ref="tagInput">
</form>
);
}
});
var TagInput = React.createClass({
getInitialState: function() {
return {
selectedTags: []
}
},
// This is called when the user types SPACE in input field
handleAddTag: function(tag) {
this.setState({
selectedTags: this.state.selectedTags.concat(tag);
});
},
render: function() {
return (
<form>
<ul>{this.state.selectedTags}</ul>
<input type="text" />
</form>
);
}
});
The above code works fine and does what is expected. The only concern is I'm using refs to directly access the Child component's internal state, and I'm not sure if this is the right "React" way.
I guess one option is to maintain the "selectedTags" state in MyForm instead of TagInput. This doesn't really make sense in my case, because in reality my form contains 5 TagInput components and many other states to manage..
Can anyone think of a way to improve my design? Or is using refs unavoidable in my case?
Thanks

You can pass handleAddTag from the parent component into the child and keep the state of the selected tags in the form component. Now when you submit the form you are pulling from the state on the form rather than using refs.
var MyForm = React.createClass({
getInitialState: function() {
return {
selectedTags: []
}
},
submit: function() {
var selectedTags = this.state.selectedTags;
$.post(
SERVER_URL,
data: { tags: selectedTags }
);
},
// This is called when the user types SPACE in input field
handleAddTag: function(tag) {
this.setState({
selectedTags: this.state.selectedTags.concat(tag);
});
},
render: function() {
return (
<form onSubmit={this.submit}>
<TagInput handleAddTag={this.handleAddTag} ref="tagInput">
</form>
);
}
});
//Use this.props.handleAddTag() to update state in Form Component
var TagInput = React.createClass({
render: function() {
return (
<form>
<ul>{this.state.selectedTags}</ul>
<input type="text" />
</form>
);
}
});
I found that using refs to get some piece of data is not as bad as using refs to modify the UI which is very bad as it will cause the UI to not be inline with your state or your application.

Related

Rendering Firebase Data in React

I'm looking to render some firebase data to the HomeFeed component. I update the state in the componentDidMount method. You can see what that looks like below. It's an array. Should I just map over that using the map function? How do I access the specific info like "title", "link", "type", etc. to be able to render it?
Thanks a lot!
var React = require('react');
var Rebase = require('re-base');
var base = Rebase.createClass("https://nimbus-8ea70.firebaseio.com/");
// TODO: Render Firebase data to screen.
// Home
// <Home />
var HomeContainer = React.createClass({
render : function() {
return (
<div className="homeContainer">
<HomeFeed />
</div>
);
}
});
// Home Feed
// <HomeFeed />
var HomeFeed = React.createClass({
componentDidMount: function() {
base.fetch('article', {
context: this,
asArray: true,
then(data){
console.log(data);
this.setState({
feed: data
})
}
});
},
getInitialState: function() {
return {
feed: []
}
},
render : function() {
return (
<div className="homeFeed">
{/* Use map function here? */}
</div>
);
}
});
module.exports = HomeContainer;
render will run whenever state has been changed (unless you modify this behavior with, say, shouldComponentUpdate) so as long as you use setState properly your component will automatically update when its state changes.
If you're asking specifically how to turn an array into something that render understands, then yes, map is a very common way to do that. It might look something like this:
render : function() {
return (
<div className="homeFeed">
{this.state.feed.map(function(ea){
return <div>{ea.someProperty}</div>
})}
</div>
);
}
Note that you have to wrap ea.someProperty in curly braces because you're basically inserting JSX inside of a JavaScript expression inside of even more JSX. This kind of nested JSX/Expression/JSX structure is something you'll have to get comfortable with in React I'm afraid.
More about array.map

how do I pass data upwards in reactjs?

Say I have an app with some path app -> taskbar -> button -> modal -> textfield. I want the textfield to be some setting a user inputs and is used elsewhere in the app, maybe app -> differentButton -> differentModal displays this user setting for example
I'm brand new to react, but it seems data can only go downwards through props, right? Is it expected that I store this state externally in a db? I don't mind doing that, but it seems like there should be an easy way to do this that I'm overlooking?
You can store the state in the parent component and pass not only the value, but also the function that modifies the value to the child. Eg:
const App = React.createClass({
getInitialState () {
return {
name: 'Dave'
};
},
render () {
return (
<div>
<MyComponent name={this.state.name} changeName={this.onChangeName} />
</div>
)
},
onChangeName (name) {
this.setState({ name });
}
});
const MyComponent = React.createClass({
propTypes: {
name: React.PropTypes.string,
changeName: React.PropTypes.func.isRequired
},
render () {
return (
<div>
<input value={this.props.name} onChange={this.props.changeName} />
</div>
);
}
});
The canonical way would be to pass a callback function from a component which is higher up in the view hierarchy through props.
That higher ordered component would encapsulate the state that you wish to modify, triggering a re-render of the sub-tree.
In your case, it looks like you would have to use App as the shared parent component for sharing state. So in App, you'd probably have a function such as:
handleTextInput: function(text) {
// handle the text input here (set some state, make an ajax call, etc)
},
And App's render function might look like this:
render: function() {
return (
<TaskBar onTextSubmit={this.handleTextInput} />
);
}
In your TaskBar component, you'd pass the callback down to Button, and so on.
Finally, in your modal component, you'd have a render function like:
render: function() {
return (
<form onSubmit={this.props.onTextSubmit}>
...
</form>
);
}
Of course, this is can quickly get quite clumsy if you have a deeply nested hierarchy, so a better approach would be to use a library for state management such as Redux.

React: Child communication in TodoList example

I'm learning React and modifying one of the tutorials. It's a Todo list, and I've come to a roadblock. I am trying to add the ability to delete items of the list. So I added an "x" to the end of each TodoList. But how can the child modify the parent's state.items? What is the "React" way of solving this?
var TodoList = React.createClass({
render: function() {
var createItem = function(itemText, index) {
return <li key={index + itemText}>{itemText} <a onClick={function() { // modify the parent item variable somehow?; }}>x</a></li>
};
return <ul>{this.props.items.map(createItem)}</ul>;
}
});
var TodoApp = React.createClass({
getInitialState: function() {
return {items: [], text: ''};
},
onChange: function(e) {
this.setState({text: e.target.value});
},
handleSubmit: function(e) {
e.preventDefault();
var nextItems = this.state.items.concat([this.state.text]);
var nextText = '';
this.setState({items: nextItems, text: nextText});
},
render: function() {
return (
<div>
<h3>TODO</h3>
<TodoList items={this.state.items} />
<form onSubmit={this.handleSubmit}>
<input onChange={this.onChange} value={this.state.text} />
<button>{'Add #' + (this.state.items.length + 1)}</button>
</form>
</div>
);
}
});
React.render(<TodoApp />, mountNode);
If you want to modify a parent's state from its child, you will need to create a function in your parent component that modifies the state in the way you want, then pass it to the child as a prop. Then, the child can just call this.props.functionName(args), and it will fire the function you created on the parent.
To follow your list example, let's say we have a List component that looks like this:
var List = React.createClass({
getInitialState : function () {
return ({items : []});
},
removeItem : function (num) {
var items = this.state.items;
items.splice(num, 1);
this.setState({items : items});
},
addItem : function () {
var value = React.findDOMNode(this.refs.itemName).value;
var items = this.state.items;
items.push(value);
this.setState({items : items});
},
render: function() {
var items = this.state.items.map(function(item, i) {
return <Item name={item} key={i} num={i} remove={this.removeItem} />
}.bind(this));
return (
<div>
List:<br/>
{items}
<br/>
<input type='text' ref='itemName'/>
<button onClick={this.addItem}>Add Item</button>
</div>
);
}
});
...and an Item component that looks like this:
var Item = React.createClass({
render : function () {
return (
<div>
{this.props.name}
<button onClick={this.props.remove.bind(null, this.props.num)}>Remove</button>
</div>
);
}
});
All this List does is hold on to the Items and provide an interface for which users can add and remove Items. Adding an Item is easy, we just need a button that, when clicked, takes the value of an <input> and adds it to our List's state. React will see the state transition and re-render the List for us, which will display the new Item.
Unlike adding an Item to the end of a list, the remove function needs to be a bit more specific regarding which Item needs to be removed. For that reason, we need a button on each Item that, when clicked, will remove the item from the list by calling this.props.remove and binding its num prop to the arguments. This will cause the removeItem function on List to fire, which will remove that item from our state. Again, React will see the state transition, and re-render our List for us, with the removed Item omitted.
Here is what that code looks like in action: https://jsfiddle.net/rxnpr9sq/
Hope that helps! Let me know if you have any additional questions.
I think this is what you need :https://facebook.github.io/react/tips/expose-component-functions.html
Michael Parker took the time to write your specific implementation this way.

How do I set state of sibling components easily in React?

I have got the beginnings of a clickable list component that will serve to drive a select element. As you can see from the below, onClick of the ListItem, I'm passing the state of a child element (ListItem in this case) to the parents (SelectableList, and CustomSelect component). This is working fine. However, what I would also like to do is change the state of the sibling components (the other ListItems) so that I can toggle their selected states when one of the ListItems is clicked.
At the moment, I'm simply using document.querySelectorAll('ul.cs-select li) to grab the elements and change the class to selected when it doesn't match the index of the clicked ListItem. This works - to an extent. However, after a few clicks, the state of the component has not been updated by React (only by client side JS), and things start to break down. What I would like to do is change the this.state.isSelected of the sibling list items, and use this state to refresh the SelectableList component. Could anyone offer a better alternative to what I've written below?
var React = require('react');
var SelectBox = require('./select-box');
var ListItem = React.createClass({
getInitialState: function() {
return {
isSelected: false
};
},
toggleSelected: function () {
if (this.state.isSelected == true) {
this.setState({
isSelected: false
})
} else {
this.setState({
isSelected: true
})
}
},
handleClick: function(listItem) {
this.toggleSelected();
this.props.onListItemChange(listItem.props.value);
var unboundForEach = Array.prototype.forEach,
forEach = Function.prototype.call.bind(unboundForEach);
forEach(document.querySelectorAll('ul.cs-select li'), function (el) {
// below is trying to
// make sure that when a user clicks on a list
// item in the SelectableList, then all the *other*
// list items get class="selected" removed.
// this works for the first time that you move through the
// list clicking the other items, but then, on the second
// pass through, starts to fail, requiring *two clicks* before the
// list item is selected again.
// maybe there's a better more "reactive" method of doing this?
if (el.dataset.index != listItem.props.index && el.classList.contains('selected') ) {
el.classList.remove('selected');
}
});
},
render: function() {
return (
<li ref={"listSel"+this.props.key}
data-value={this.props.value}
data-index={this.props.index}
className={this.state.isSelected == true ? 'selected' : '' }
onClick={this.handleClick.bind(null, this)}>
{this.props.content}
</li>
);
}
});
var SelectableList = React.createClass({
render: function() {
var listItems = this.props.options.map(function(opt, index) {
return <ListItem key={index} index={index}
value={opt.value} content={opt.label}
onListItemChange={this.props.onListItemChange.bind(null, index)} />;
}, this);
return <ul className="cs-select">{ listItems }</ul>;
}
})
var CustomSelect = React.createClass({
getInitialState: function () {
return {
selectedOption: ''
}
},
handleListItemChange: function(listIndex, listItem) {
this.setState({
selectedOption: listItem.props.value
})
},
render: function () {
var options = [{value:"One", label: "One"},{value:"Two", label: "Two"},{value:"Three", label: "Three"}];
return (
<div className="group">
<div className="cs-select">
<SelectableList options={options}
onListItemChange={this.handleListItemChange} />
<SelectBox className="cs-select"
initialValue={this.state.selectedOption}
fieldName="custom-select" options={options}/>
</div>
</div>
)
}
})
module.exports = CustomSelect;
The parent component should pass a callback to the children, and each child would trigger that callback when its state changes. You could actually hold all of the state in the parent, using it as a single point of truth, and pass the "selected" value down to each child as a prop.
In that case, the child could look like this:
var Child = React.createClass({
onToggle: function() {
this.props.onToggle(this.props.id, !this.props.selected);
},
render: function() {
return <button onClick={this.onToggle}>Toggle {this.props.label} - {this.props.selected ? 'Selected!' : ''}!</button>;
}
});
It has no state, it just fires an onToggle callback when clicked. The parent would look like this:
var Parent = React.createClass({
getInitialState: function() {
return {
selections: []
};
},
onChildToggle: function(id, selected) {
var selections = this.state.selections;
selections[id] = selected;
this.setState({
selections: selections
});
},
buildChildren: function(dataItem) {
return <Child
id={dataItem.id}
label={dataItem.label}
selected={this.state.selections[dataItem.id]}
onToggle={this.onChildToggle} />
},
render: function() {
return <div>{this.props.data.map(this.buildChildren)}</div>
}
});
It holds an array of selections in state and when it handles the callback from a child, it uses setState to re-render the children by passing its state down in the selected prop to each child.
You can see a working example of this here:
https://jsfiddle.net/fth25erj/
Another strategy for sibling-sibling communication is to use observer pattern.
The Observer Pattern is a software design pattern in which an object can send messages to multiple other objects.
No sibling or parent-child relationship is required to use this strategy.
Within the context of React, this would mean some components subscribe to receive particular messages and other components publish messages to those subscribers.
Components would typically subscribe in the componentDidMount method and unsubscribe in the componentWillUnmount method.
Here are 4 libraries that implement the Observer Pattern. The differences between them are subtle - EventEmitter is the most popular.
PubSubJS: "a topic-based publish/subscribe library written in JavaScript."
EventEmitter: "Evented JavaScript for the browser." It's actually an implementation of a library that already exists as part of nodejs core, but for the browser.
MicroEvent.js: "event emitter microlibrary - 20lines - for node and browser"
mobx: "Simple, scalable state management."
Taken from: 8 no-Flux strategies for React component communication which also is a great read in general.
The following code helps me to setup communication between two siblings. The setup is done in their parent during render() and componentDidMount() calls.
class App extends React.Component<IAppProps, IAppState> {
private _navigationPanel: NavigationPanel;
private _mapPanel: MapPanel;
constructor() {
super();
this.state = {};
}
// `componentDidMount()` is called by ReactJS after `render()`
componentDidMount() {
// Pass _mapPanel to _navigationPanel
// It will allow _navigationPanel to call _mapPanel directly
this._navigationPanel.setMapPanel(this._mapPanel);
}
render() {
return (
<div id="appDiv" style={divStyle}>
// `ref=` helps to get reference to a child during rendering
<NavigationPanel ref={(child) => { this._navigationPanel = child; }} />
<MapPanel ref={(child) => { this._mapPanel = child; }} />
</div>
);
}
}

Sending events between components

Consider the ToDo App example on the React homepage. For posterity, here's a fiddle and the code is at the end of this post.
Now say we decide to upgrade this app with w simple features:
Each todo item will have not only text, but also a "done" attribute. You can click on an item and it will toggle the "done" state, and perhaps add strikethrough styling when it is done.
At the very bottom, there will be text indicating the number of "Done", eg, "2 items done, 3 left to do"
The problem is that the state of the items is maintained in TodoApp, not in TodoList. So we'd like to add an onClick={something} to the <li> element in TodoList's render method. But we want that click event to be handled by TodoApp, which would then change the state of the item, and cause everything to re-render. If we wanted to approach it like this, how could we do it?
We could also create a TodoItem component to be called by TodoList, and push the statefulness down into that. This would allow the click to be handled by the TodoItem, but now we would need a way to share the TodoItems' states with the component indicating the number of items done and still todo.
In a nutshell, I'd like to know how components can send events to each other, because I think just knowing that would allow solutions to both problems.
React ToDo App
/** #jsx React.DOM */
var TodoList = React.createClass({
render: function() {
var createItem = function(itemText) {
return <li>{itemText}</li>;
};
return <ul>{this.props.items.map(createItem)}</ul>;
}
});
var TodoApp = React.createClass({
getInitialState: function() {
return {items: [], text: ''};
},
onChange: function(e) {
this.setState({text: e.target.value});
},
handleSubmit: function(e) {
e.preventDefault();
var nextItems = this.state.items.concat([this.state.text]);
var nextText = '';
this.setState({items: nextItems, text: nextText});
},
render: function() {
return (
<div>
<h3>TODO</h3>
<TodoList items={this.state.items} />
<form onSubmit={this.handleSubmit}>
<input onChange={this.onChange} value={this.state.text} />
<button>{'Add #' + (this.state.items.length + 1)}</button>
</form>
</div>
);
}
});
React.renderComponent(<TodoApp />, document.body);
The idiomatic way to do this is to pass a callback down to TodoList:
Live demo: http://jsbin.com/zeqizene/1/edit
I've changed TodoList to look like this:
var TodoList = React.createClass({
handleDoneToggle: function(i) {
this.props.onDoneToggle(i);
},
render: function() {
var createItem = function(item, i) {
return <li onClick={this.handleDoneToggle.bind(null, i)}>
{item.text}
{item.done && " (done)"}
</li>;
};
return <ul>{this.props.items.map(createItem, this)}</ul>;
}
});
When an item is clicked, TodoList will call its own onDoneToggle function, so TodoApp can modify the state appropriately.
See also Editing a rich data structure in React.js.

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