It is working fine here.
You should check the data in your props if there is any `flag` key or not and if there is a `flag` key check that if it is `AAA` or not.
<!-- begin snippet: js hide: false console: true babel: true -->
<!-- language: lang-js -->
class App extends React.Component {
constructor() {
super();
this.state = {
data: "aa"
};
}
/*
1. props.data is coming from mapping component state to redux connect
2. connect file and selectors are alright, because other parts of this component
work as expected, and even same props.data is used elsewhere in the component
3. a method wihtout input as in showAnotherComponent = () => false; will hide the
AnotherComponent element successfully. but even sth like
showAnotherComponent = (data) => false; will not work!!!
4. props.data is properly injected to the render method, console.log(props.data) in reder
method will display updated value.
5. props.data is never null or undefined and so on ..
*/
showAnotherComponent = data => data.flag === "AAA";
render() {
console.log(this.props.data); // will show the updated props.data
return (
<div className="row">
<div className="col-md-10">
<h1>Some heading</h1>
</div>
<div className="col-md-2">
{/* the element in next line will always show up invariably, whatever the
content of props.data. tried ternary, same result. */}
{this.showAnotherComponent({ flag: this.state.data }) && (
<div>asdsdasd</div>
)}
</div>
<button onClick={() => this.setState({ data: "AAA" })}>Toggle</button>
</div>
);
}
}
ReactDOM.render(<App />, document.body);
<!-- language: lang-html -->
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/16.6.3/umd/react.production.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react-dom/16.6.3/umd/react-dom.production.min.js"></script>
<!-- end snippet -->
Click on Toggle and the Data will be displayed.
That's *property spread notation*. It was added in ES2018, but long-supported in React projects via transpilation (as "JSX spread attributes" even though you could do it elsewhere, too, not just attributes).
`{...this.props}` *spreads out* the "own" properties in `props` as discrete properties on the `Modal` element you're creating. For instance, if `this.props` contained `a: 1` and `b: 2`, then
<Modal {...this.props} title='Modal heading' animation={false}>
would be the same as
<Modal a={this.props.a} b={this.props.b} title='Modal heading' animation={false}>
But it's dynamic, so whatever "own" properties are in `props` are included.
Since `children` is an "own" property in `props`, spread will include it. So if the component where this appears had child elements, they'll be passed on to `Modal`. Putting child elements between the opening tag and closing tags is just syntactic sugar — the good kind — for putting a `children` property in the opening tag. Example:
<!-- begin snippet: js hide: true console: true babel: true -->
<!-- language: lang-js -->
class Example extends React.Component {
render() {
const { className, children } = this.props;
return (
<div className={className}>
{children}
</div>
);
}
}
ReactDOM.render(
[
<Example className="first">
<span>Child in first</span>
</Example>,
<Example className="second" children={<span>Child in second</span>} />
],
document.getElementById("root")
);
<!-- language: lang-css -->
.first {
color: green;
}
.second {
color: blue;
}
<!-- language: lang-html -->
<div id="root"></div>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/16.6.3/umd/react.production.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react-dom/16.6.3/umd/react-dom.production.min.js"></script>
<!-- end snippet -->
Spread notation is handy not only for that use case, but for creating a new object with most (or all) of the properties of an existing object — which comes up a lot when you're updating state, since you can't modify state directly:
this.setState(prevState => {
return {foo: {...prevState.foo, a: "updated"}};
});
That replaces `this.state.foo` with a new object with all the same properties as `foo` except the `a` property, which becomes `"updated"`:
<!-- begin snippet: js hide: true console: true babel: false -->
<!-- language: lang-js -->
const obj = {
foo: {
a: 1,
b: 2,
c: 3
}
};
console.log("original", obj.foo);
// Creates a NEW object and assigns it to `obj.foo`
obj.foo = {...obj.foo, a: "updated"};
console.log("updated", obj.foo);
<!-- language: lang-css -->
.as-console-wrapper {
max-height: 100% !important;
}
<!-- end snippet -->
[1]: https://reactjs.org/docs/jsx-in-depth.html#children-in-jsx
