The componentDidMount is not getting called in reactjs - json

Question

I'm trying the example in reactjs tutorial https://facebook.github.io/react/docs/tutorial.html to read the json from server(file). But, my "componentDidMount" is not getting called.
Below is the code:
var CommentBox = React.createClass({
loadCommentsFromServer: function() {
$.ajax({
url: this.props.url,
dataType: 'json',
success: function(data) {
this.setState({data: data});
}.bind(this),
error: function(xhr, status, err) {
console.error(this.props.url, status, err.toString());
}.bind(this),
cache: false
});
},
getInitialState: function() {
return {data: {}};
},
componentDidMount: function() {
this.loadCommentsFromServer();
},
render: function() {
return (
<div className="commentBox">
<h1>Comments</h1>
<CommentList data={this.state.data} />
</div>
);
}
});
var CommentList = React.createClass({
render: function() {
var commentNodes = this.props.data.content.map(function(comment) {
return (
<Comment pageName={comment.xyz} key={comment.id}>
{comment.abc}
</Comment>
);
});
return (
<div className="commentList">
{commentNodes}
</div>
);
}
});
var Comment = React.createClass({
render: function() {
return (
<div className="comment">
<h2 className="commentpageName">
{this.props.pageName}
</h2>
<p> {this.props.children} </p>
</div>
);
}
});
ReactDOM.render(<CommentBox url="/api/comments" />, document.getElementById('content'));
Please check the way I have initialized the data(data: {})
The "componentDidMount" gets called when the json is of the following type(Just the way in the tutorial):
[ {"id": "1", "xyz": "xyz1", "abc": "abc1"},
{"id": "2", "xyz": "xyz2", "abc": "abc2"} ]
But the json format I want is:
{
content: [
{"id": "1", "xyz": "xyz1", "abc": "abc1"},
{"id": "2", "xyz": "xyz2", "abc": "abc2"},
{"id": "3", "xyz": "xyz3", "abc": "abc3"}],
"totalPages":3,
"totalElements":10,
"last":true
}
Let me know in what conditions the componentDidMount doesn't get called. Please help.
In the "Networks" console of chrome developer tools, I don't see the call made to my json file.
When I added logs in my program, I see that getInitialState() gets called first, then render, then the error "Uncaught TypeError: Cannot read property 'data' of null" is shown.

Answer 1

I think your componentDidMount() is not called because your render code inside <CommentList> does not work on first render, because data is empty, and this.props.data.content probably does not exist, therefore your render fails.
What you probably should do is change this:
var commentNodes = this.props.data.content.map(function(comment) {
To this:
var commentNodes = [];
if (this.props.data.content) {
commentNodes = this.props.data.content.map(function(comment) {
...
}
componentDidMount() is always called after the first render (and not in subsequent renders)