$.post(url, data) doesn't work - json

Question

I'm creating simple twitter_clone using Rails to create json API and ReactJS in frontend.
What I need now is to save new created tweet into DB and then to update an API in json which contain list of tweets to be able to use them to render a view.
To achieve it I try to use post request:
My add tweet function in main.jsx file
addTweet(tweetToAdd){
$.post("/tweets", { body: tweetToAdd }) //after saving to database
.success( savedTweet => {
let newTweetsList = this.state.tweetsList;
newTweetsList.unshift(savedTweet);
this.setState({tweetsList: newTweetsList});
})
.error(error => console.log(error));
}
There is a problem with delivering body of the tweet to database, cause after submitting there is NULL here.
Probably it means that body isn't send to DB ,but rest of parameters there are.
in /tweets there is an json API which looks like:
[{"id":17,"user_id":1,"body":null,"created_at":"2015-12-18T10:11:25.085Z","updated_at":"2015-12-18T10:11:25.085Z","name":"Marek Czyż"}]
When I create tweet manually form console everything works. so the problem must have been in previous piece of code.
Secondly after pressing SUBMIT tweet Ive recevied a warning that
Warning: Each child in an array or iterator should have a unique "key" prop. Check the render method of TweetList. See fb.me/react-warning-keys for more information.
although Ive got a key to every Tweet:
let tweets = this.props.tweets.map(tweet => );
Please, help me.

Answer 1

Assuming you're passing the right value as tweetToAdd, make sure you permit the body param in your controller. If it works in the console, it's not a validation problem, rather an unpermitted param.
As for the error you're seeing, you'll need to add a key prop to each rendered tweet. Something like:
render() {
let tweets = this.props.tweets;
return <ul>
{tweets.map(tweet => {
return <li key={tweet.id}>{tweet.body}</li>;
})}
</ul>;
}