I'm trying to do Step 15 of this ReactJS tutorial: React.js Introduction For People Who Know Just Enough jQuery To Get By
The author recommends the following:
overflowAlert: function() {
if (this.remainingCharacters() < 0) {
return (
<div className="alert alert-warning">
<strong>Oops! Too Long:</strong>
</div>
);
} else {
return "";
}
},
render() {
...
{ this.overflowAlert() }
...
}
I tried doing the following (which looks alright to me):
// initialized "warnText" inside "getInitialState"
overflowAlert: function() {
if (this.remainingCharacters() < 0) {
this.setState({ warnText: "Oops! Too Long:" });
} else {
this.setState({ warnText: "" });
}
},
render() {
...
{ this.overflowAlert() }
<div>{this.state.warnText}</div>
...
}
And I received the following error in the console in Chrome Dev Tools:
Cannot update during an existing state transition (such as within
render
or another component's constructor). Render methods should be a pure function of props and state; constructor side-effects are an anti-pattern, but can be moved tocomponentWillMount
.
Here's a JSbin demo. Why won't my solution work and what does this error mean?
See Question&Answers more detail:os