yield from callback function/event listener?

Is there a way to yield from callback function. e.g.

function* mySaga() {
    hashHistory.listenBefore(location => {
        yield put({ type: 'LOCATION_CHANGE', payload: location });
        var state = yield select();
        return true; // or false depending on state
        // or do some more yield stuff        
    });
}

How do you handle this kind of side effects?

[evgenyt1]

@yelouafi I spent few days trying and debugging a bunch of ways, including generating and handling promises, using callbacks, etc. However all of this complicated my code much and was unreliable (as I want different sagas handle different routes and depend on each other result).

My workaround is not to use sagas in this case. Just a special list or routing handlers, that are called synchronously in predictable order by some general entry point (events of router), get state/dispatch and routing stuff as parameters, with final “fallback” handler that just approves user navigation (it wasn’t handled by routing handlers).

In my case I have a routing directory in src with handleAuth.js, handlePage1.js, handlePage2.js etc. So the order is also important, and event handlers can depend on other handler result. As auth goes first, than page handlers that can fetch some data from store, redirect (using dispatch), etc etc

[zalmoxisus]

Hey @evgenyt1.

One solution would be to use channels as described on SO. It is also planned to be supported out of the box.

Another solution would be just to use dispatch (and getState in your case) parameters passed into rootSaga. Though it seems uglier than above one, I usually use this solution for binding events. A bit harder to test, but cleaner and guaranteed that you’ll not miss any event.