React: Children onclick to change parent's state for re-rendering - reactjs

Question

I'm really new with react. I'm trying to get the parent to change page displayed depending on the states. I have a button in my sub-component that should send "true" or "false" to the parent component so it knows if to render it or not. I think it should be done with props like this:
this.state = {
btnNewScreen: this.props.btnNewScreen //true or false
};
But im not getting it to work. Could you give any tips? Here is the full parent - child
parent - maindisplay.js
import React from 'react';
import Mainpage_Addscreen from '../components/subcomponents/mainpage-addscreen';
import Mainpage_Showscreens from '../components/subcomponents/mainpage-showscreens';
//
class MainDisplay extends React.Component {
constructor() {
super();
this.state = {
btnNewScreen: false //should be this.props.btnNewScreen?
};
}
render() {
var renderThis;
if (!this.state.btnNewScreen) {
renderThis =
<div>
<Mainpage_Addscreen />
<Mainpage_Showscreens />
</div>
}
else {
//renderThis = <AddScreen />
renderThis =
<div>
<Mainpage_Addscreen />
<h3>Change to this when true (button click)</h3>
</div>
}
return (
<div>
{renderThis}
</div>
);
}
}
export default MainDisplay;
child - mainpage-addscreen.js
import React from 'react';
import Glyphicon from 'react-bootstrap/lib/Glyphicon';
import Button from 'react-bootstrap/lib/Button';
class Mainpage_Addscreen extends React.Component {
constructor() {
super();
this.state = {
btnNewScreen: true
};
this.newScreen = this.newScreen.bind(this);
}
newScreen(e) {
this.setState({ btnNewScreen: !this.state.btnNewScreen });
console.log(this.state.btnNewScreen);
}
render() {
var text = this.state.btnNewScreen ? 'Add new' : 'Screens';
return (
<div className="main_window col-sm-offset-1 col-sm-10">
<h3 id="addscreens">Screens: </h3>
<Button id="addScreen" className="btn btn-primary dropdown-toggle" type="button" data-toggle="dropdown" onClick={this.newScreen}><Glyphicon id="refresh_screens" glyph="plus" /> {text}</Button>
</div>
);
}
}
export default Mainpage_Addscreen;

Answer 1

What you need to do is to pass a method from the parent to the child, That it can call when the button is clicked. This method that belongs to the parent will change the state.
In MainPage.js
changeButtonState(event) {
this.setState({btnNewScreen: !this.state.btnNewScreen})
}
pass this method to your child component as
<Mainpage_Addscreen buttonClick={this.changeButtonState.bind(this)} />
and finally in the child component,
<Button .... onClick={this.props.buttonClick} />

Answer 2

What you probably need is a callback function, which your parent passes as a prop to your child, and that your child can then call.
Something like this:
// In parent
constructor() {
...
this.onChildClicked = this.onChildClicked.bind(this);
}
onChildClicked() {
this.setState({childWasClicked : True });
}
render() {
...
return (
<div>
<Child onClicked={this.onChildClicked} />
</div>
)
}
// In child
render() {
...
return (
<div>
<button onClick={this.props.onClicked} />
</div>
)
}
PS: I notice that you have a capitalized <Button> component. This is typically for components that you have defined yourself. Standard DOM elements take lowercase, e.g. <div>, <p> etc