As an example (real tried code)
I have a component of which I want to initiate a NEW instance for rendering.
import React, { Component } from 'react';
export default class TinyObject extends Component {
constructor(props) {
super(props);
console.log("TinyObject constructor");
}
render() {
console.log("TinyObject render");
return (
<div>HEY THIS IS MY TINY OBJECT</div>
);
}
}
Then in main App constructor I do the following:
var myTinyObject = new TinyObject();
var myArray = [];
myArray.push(myTinyObject);
this.state = {testing: myArray};
Then a created a function to render this:
renderTest()
{
const {testing} = this.state;
const result = testing.map((test, i) => {
console.log(test);
return {test};
});
}
And I call this from the App render function like this:
render() {
const { gametables, tableActive } = this.state;
console.log("render");
return <div><div>{this.renderTest()}</div></div>;
}
It runs, no errors.
I see console log of the following:
console.log("TinyObject constructor");
console.log(test);
But I don't see console log of the TinyObject render nor do I see the render output.
Thanks to lustoykov answer I got a little further
JSX: var myTinyObject = <TinyObject />;
works!
but in the real app I add a little more and don't know how to do it here.
return <GameTable key={'gt'+index} data={table} settings={this.settingsData} sendTableNetworkMessage={this.sendTableNetworkMessage} />
this is the way I was rendering; and I needed more instances of GameTable
now the question is; how do I add the arguments like data & settings to myTinyObject.
thanks for helping so far.
You don't manually instantiate react component, use JSX or createElement. For instance
via JSX
var myTinyObject = <TinyObject prop1={prop1} prop2={prop2} />;
via React.createElement
var myTinyObject = React.createElement(TinyObject, { prop1, prop2 }, null);
I would definitely check out some tutorials and how React works at a basic level. You aren't really going to call your react components like you would normally do in javascript since the render function returns jsx.
Fundamentally, React is what is called a single page application. That means that your browser will load up a single html file with a div. Now that div will be where React performs its magic by using Javascript to change stuff around.
It is easiest for me to think of React as a tree. You create these components that you place on the DOM or in your HTML and React will add and remove them downwards. For instance, take a look at this picture of twitter.
So first the Feed component is going to be put on the DOM. Then the Feed component will render the Tweet components. So as you can see the rendering goes in one direction, downwards.
Now, as you can see your render methods are not returning javascript. It is returning something that looks like HTML but we call it JSX. That means we want to render it a little differently with our react classes.
If we have a child component:
class Child extends React.Component {
render() {
return <h1>Hello, I am inside the parent component</h1>;
}
}
We can call the render method like this:
class Parent extends React.Component {
render() {
<Child /> //This is how I use the Child class
}
}
Now the reason why react is so performant is that the child cannot be re-rendered unless we do 1 of two things:
It is a component with a state and we call a method setState()
We pass down new props to a child component from the parent component
You can read about it here
Now the only way to get React to call that render function again is by doing those two things.
Related
I would like to call a method on a random component after creating it but before rendering it. To perform child specific calculations for the parent prior to rendering the parent. A simple static should work.
class Container extends ReactWrapper{
render() {
const rClass = React.createClass(this.getCCArgs());
var newData = rClass.expectedUtilityFunction(data);
// render parent with new data.
return (<div {...this.props.data, ...newData}>
{rClass}
</div>);
};
};
Tried a number of ways and the utility method is always not found.
I could push things up the line logically and add a method to return the class used to create the react instance from the input data but I already have the react class instance.
React.createClass is deprecated and removed from React 16+. So I suggest stop tring to make it work.
Your code is good fit for High order component.
Below is sample code (I didn't tested it, so use it as hint only)
function WrappedComponent (Component, props) {
var newData = /* Here is good place for expectedUtilityFunction code. Don't put expectedUtilityFunction function into Component, put it here, in HOC body */
// render parent with new data.
return (<div {...props.data, ...newData}>
<Component/>
</div>);
}
And use HOC like this
class Container extends ReactWrapper{
constructor(props) {
supre(props);
// Assuming that this.getCCArgs() returns component
this.hoc = WrappedComponent (this.getCCArgs(), props);
}
render() {
return this.hoc;
}
}
I have the following use case.
Some HTML from a third party source is loaded inside my React component:
class MyComponent extends Component {
render() {
return (
<div
dangerouslySetInnerHTML={{ __html: this.props.externalHTML }}
/>
);
}
}
Inside the externally loaded HTML a click event exists for a specific span, which is supposed to call a callback function that exists in my application.
<span onclick="myCallback(param1='asd', param2=123, param3='asdas')">
Click me!
</span>
Where should I put this myCallback function?
If I place it inside the component class I get the following error when clicking the span, because as I understand the function is not visible to the externally loaded HTML: Uncaught ReferenceError: myCallback is not defined at HTMLSpanElement.onclick
My other idea was to add the function to the window object window.myCallback = ... inside my main index.js file to be loaded every time the app loads. This way it works but I have two issues.
My understanding is that this is not the correct React way to do it.
Whenever I click the span element the callback function is triggered twice and I cannot understand why.
Any suggestions?
Using "dangerouslySetInnerHTML" is ..."dangerous" as its name ^^, which is actually not pure React way, either.
However, If you have to do it, you can do something like this (take advantage of built-in jQuery inside React be default)
=====
EDITED VERSION FROM HERE: (use only 1 component)
export default class MyComponent extends Component {
componentDidMount() {
// using jQuery to manipulate DOM element form third-party source
// NB. you may think of using setTimeout here, to wait for the external source to be fully loaded here, of course it's not so safe
// but anyway, we are using "dangerouslySetInnerHTML" anyway => quite dangerous, though ^^
// setTimeout(function(){
$(document.findElementsByTagName("span")[0]).click(function(e){
// or perhaps $("#spanID").click if you can, just be careful between DOM element and react component
e.preventDefault();
// DO SOMETHING HERE, just like you do in the window.onload function
// or maybe you also need to get param values by getting $(this).data("...") or $(this).attr("ATTRIBUTE-NAME")
return false;
});
// });
}
render() {
return (
<div
dangerouslySetInnerHTML={{ __html: this.props.externalHTML }}
/>
);
}
}
=====
OLD ANSWER FROM HERE: (use 2 components)
ParentComponent:
export default class MyComponent extends Component {
constructor(props) {
super(props);
this.callbackOnThisComponent = this.callbackOnThisComponent.bind(this);
}
callbackOnThisComponent(param1, param2, param3) {
// do whatever you like with the above params
}
render() {
return (
<ChildComponent triggerCallbackOnParent={this.callbackOnThisComponent} />
);
}
}
ChildComponent:
export default class ChildComponent extends Component {
componentDidMount() {
// using jQuery to manipulate DOM element form third-party source
let that = this;
// NB. you may think of using setTimeout here, to wait for the external source to be fully loaded here, of course it's not so safe
// but anyway, we are using "dangerouslySetInnerHTML" anyway => quite dangerous, though ^^
$(document.findElementsByTagName("span")[0]).click(function(e){
// or perhaps $("#spanID").click if you can, just be careful between DOM element and react component
e.preventDefault();
that.props.triggerCallbackOnParent(param1, param2, param3);
// or maybe you need to get param values by getting $(this).data("...") or $(this).attr("ATTRIBUTE-NAME")
return false;
}, that);
}
render() {
return (
<div
dangerouslySetInnerHTML={{ __html: this.props.externalHTML }}
/>
);
}
}
I just use the main React's idea, which is passing props downward to children components, and when you want to trigger a function upward from child component, create a callback function on parent. For your or anyone else's reference, this is my demonstration on how to pass callback function from parent to multi-level-children components:
Force React container to refresh data
Re-initializing class on redirect
if this doesn't work yet, feel free to show me some error logs, thanks
i got a component A:
import React, { Component } from 'react'
import Gmap from '../global/gmap.component'
class RandomPlace extends Component {
render() {
return (
<Gmap address={this.state.random.location} />
which renders among other things, the Gmap component:
class Gmap extends Component {
componentDidMount () {
}
render() {
return (
<div className="gmap-component">
<p>{this.props.address}</p>
This <p>{this.props.address}</p> is well displayed and updated when i hit a "reload" button on component A. At this point, the React Chrome extension shows well the props' address content. And sees it being updated well on the "reload" action.
Problem is, i cant seem to be able to reach the props property address in the internal functions of my component Gmap like componentDidMount() or aCustomFunction().
I have tested this:
componentDidMount () {
console.log('gmap did mount')
this.setState({address: this.props.address})
let x = this.props.address
let y = this.state.address
console.log(x)
console.log(y)
With a constructor at the top of the class:
constructor (props) {
super(props)
this.state = {
address: 'xx'
}
But nothing shows up. I am new to React and sure i am missing something pretty basic but cant see to spot it.
Thanks in advance.
Are you asking how to call a custom function on your child component? If so,
<Gmap address={this.state.random.location} ref={(map) => { this.map = map; }} />
Then
this.map.aCustomFunction()
I'm not entirely sure, but i think it's going like:
In your component A, address={this.state.random.location} set from the state, as you see.
random object fill with call getRandomPlace() in componentDidMount().
So what's going on: at first you render Gmap component you have prop address there with undefined, because on component A didn't call componentDidMount() yet.
Then in component A trigger componentDidMount you get filled object "random" and yuor component Gmap recive normal prop addres, with no indefined. And rerender component with this new adderss prop, but your componentDidMount() in component Gmap has already invoked and doesn't trigger more...
If i'm right, you can set at component A
constructor(){
super();
this.state={
random: {location: "some test value"}
}
}
and you will see this "some test value" instead undefined in your console log.
I am using same component multiple times in the same page, and I just realized that any event dispatched are intercepted by all the same companents and all the components are updated together.
This is not acceptable, as even if it is same component, if it is used to display different data, they should have totally independent behavior. Action performed in one component should never be listened by another component.
How can I fix this error?
You should have a container component which will get a data collection, which represents the component you are repeating. An action will change that data collection, and not the repeated component itself. In other words, the repeated component should not get data directly from the store.
You could see an full todomvc example, which has the same "TodoItem" component being rendered a few times in one page here: TodoMVC example
Example:
var ButtonStore = require('../stores/ButtonStore');
function getButtonState() {
return {
allButtons: ButtonStore.getAll()
}
}
const Button = (props) => {
return <button>{props.text}</button>
}
class ButtonList extends React.Component {
constructor(props) {
super(props)
this.state = getButtonState()
}
render() {
return <div>
{this.state.allButtons.map(button => <Button {...button} />)}
</div>
}
}
Here is a fiddle of the example, just without the store: Component List Example
It could be helpful, if you post some code example.
I am struggling currenlty with iScroll in combination with reactJS.
This code samples are written in typescript.
I created a wrapper class for iScroll:
import * as React from 'react';
import * as ReactDOM from 'react-dom';
var iScroll = require('iscroll');
...
componentDidMount() {
this._initializeIScrollInstance();
console.log(this);
}
_initializeIScrollInstance() {
setTimeout(() => {
let element = ReactDOM.findDOMNode(this);
const iScrollInstance = new iScroll(element, this.props.options);
this._iScrollInstance = iScrollInstance;
}, 100);
}
render() {
return (
<div style={ this.props.style } >
{ this.props.children }
</div>
)
}
}
Then I use it like this in my sidebar class for instance.
<ScrollWrapper>
<SidebarMenu toggle={ this.toggle.bind(this) } />
</ScrollWrapper>
The problem I am facing is when I toggle a menu inside my sidebar. This means the height changes so I need to call the refresh methode for iScroll.
But how can I achieve this?
Can I get the _iScrollInstance in my parent component?
Its possible to keep a state inside my sidebar and pass it down to the ScrollWrapper as a property and watch for it in componentReceiveProps.
But this sounds like a cheap solution to me.
Anyone maybe have a better solution for that kind of problem?
Based on your code :
<ScrollWrapper>
<SidebarMenu toggle={ this.toggle.bind(this) } />
</ScrollWrapper>
I see the child component action (toggle) needs to do something with the parent component (scroll). The idiomatic way to do this is for the parent to give the child component a function (callback) that the child calls when it wants something in the parent to change.
Note: The recommeded way is to use flux ... but thats a whole other topic (lookup redux which is what I use).