Conditional Subscriptions

[estaylorco]

Conditional Subscriptions

[ifandelse]

Thanks! You're in luck - this is actually possible now:

var channel = postal.channel( 'ui' );
var sub = channel.subscribe( topics.POPOVER_CLOSE, function( envelope ) { close( envelope ); } )
                          .withContext( this.busContext )
                          .withConstraint( function( envelope ) {
                              return envelope.target === 'globalActionsPopover';
                          });

The function you pass to withConstraint is a predicate - returning true if you want the subscription callback to fire or false if not. IIRC, the current postal API allows for multiple constraints to be registered via withConstraints([pred1, pred2, pred3]), etc. Be aware that this will most likely change with future postal 0.9.x (which hasn't stabilized yet). Future postal 0.9.x will actually provide a pipeline hook to allow you to make adding predicate constraints like this much more expressive.

Check out the SubscriptionDefinition API Documentation to see what members on the prototype can be called to further configure a subscription....

[estaylorco]

That's just awesome! I don't know how I missed this. Thank you!