Meteor React container error handling

Handling errors from Meteor subscriptions using React as frontend.

There are two different ways to create a container:

• using meteor/react-meteor-data, a native approach
• using arunoda/react-komposer

meteor/react-meteor-data

Master branch
See App.jsx

Error handling is made possible by using ReactiveVar. error variable is defined in the App module.
This variable should be used in withTracker method where the dependency is registered:

export default withTracker((props) => {
    ...
    return {
        error: error.get(),
        ...
    };
})(App)

And used in render() function:

render() {
    var e = error.get();
    if (e) {
        content = (<div>Sorry, mate. You just got errored. {e.message}</div>)
    }
    ...
}

Summary
In this approach props are returned in the withTracker function. Error handling is entirely in that function. Some considerations are required if we want to prevent endless loop.

Pros:

• better for containers where no error handling is necessary

Cons:

• module variable (error = ReactiveVar(null)) must be used to handle errors
• when handling the errors, some things are returned, some updated through reactive vars

arunoda/react-komposer

Komposer branch
See App.jsx

Error handling and data fetching are handled in function passed to container function:

export default container(function (props, onData) {
    const taskHandle = Meteor.subscribe('tasks', {
        onError: function (err) {
            onData(null, {
                error: err
            });
        }
    });

    if (taskHandle.ready()) {
        onData(null, {
            tasks: Tasks.find({}, {sort: {createdAt: -1}}).fetch(),
            currentUser: Meteor.user()
        });
    }
    else {
        onData(null, {
            loading: true
        });
    }
}, App);

Summary
Everything is handled in function passed to container.

Pros:

• data & error handling done consistently (onData callback, no return value)
• no module variables

Cons:

• somewhat more complex container function