{"id":980,"date":"2023-05-22T05:00:00","date_gmt":"2023-05-22T12:00:00","guid":{"rendered":"https:\/\/www.angulartraining.com\/daily-newsletter\/?p=980"},"modified":"2023-05-19T20:42:15","modified_gmt":"2023-05-20T03:42:15","slug":"rxjs-tapobserver","status":"publish","type":"post","link":"https:\/\/www.angulartraining.com\/daily-newsletter\/rxjs-tapobserver\/","title":{"rendered":"RxJs TapObserver"},"content":{"rendered":"\n

In my last post, I covered how we can define multiple callback functions when subscribing<\/a> to an Observable (next<\/code>, error<\/code>, complete<\/code>). I mentioned that those callbacks are available when we call the subscribe()<\/code> method, which goes against our philosophy of avoiding subscriptions as much as possible because they can lead to memory leaks<\/a>.<\/p>\n\n\n\n

In previous newsletters, I covered how the tap<\/code> operator<\/a> can help avoid subscriptions by “spying” on an Observable.<\/p>\n\n\n\n

Well, tap<\/code> is a simple gift that keeps on giving. The operator supports an TapObserver<\/a><\/code> interface that can be used instead of the callback function we used in our earlier examples<\/a>:<\/p>\n\n\n

\n
\"\"<\/figure>\n<\/div>\n\n\n

<\/p>\n\n\n\n

As a result, we can register several side effects in our code based on any of these notifications as follows:<\/p>\n\n\n

\n
\"\"<\/figure>\n<\/div>\n\n\n

<\/p>\n\n\n\n

Most of these notifications are explicit in what they do, but let’s document all six of them for the sake of clarity:<\/p>\n\n\n\n