Avoiding the insertion of duplicates in Angular 2 with Observables

My current issue involves a growing array each time I submit a post. It seems like the problem lies within the second observable where the user object gets updated with a new timestamp after each post submission.

I have attempted to prevent duplicate entries in the array by checking if the post already exists inside the observable, but this approach doesn't seem to be effective.

 fetchPosts(url: string) {
    switch (url) {
        case '/timeline/top':
            this.postsService.fetchAllPosts(this.selectedArea)
                .subscribe(posts => {
                    let container = new Array<PostContainer>();
                    for (let post of posts) {
                        this.getUserEquippedItems(post.username).subscribe(x => {
                                try {
                                    if (container.indexOf(new PostContainer(post, x[0].equippedItems)) === -1) {
                                        container.push(new PostContainer(post, x[0].equippedItems));
                                    }
                                     console.log( container); // encountering exponential growth after each submitted post
                                } catch (ex) { }
                            }
                        );
                    }
                    this.postContainers = container; // postContainers is the array being iterated over in the frontend.
                });
            break;
   }

}

Answer №1

There is uncertainty about whether you are accurate in identifying the issue, but eliminating duplicates from your posts can be as straightforward as this:

this.postsService.subscribeAllPosts(this.selectedArea)
            .distinct()
            .subscribe(posts => {
                ...
            });

Answer №2

The issue lies in the fact that when you create a new instance of PostContainer, it is a separate object not within the scope of container. This causes every post to be added to posts.

To resolve this, you should verify that a unique value of post does not already exist in any item of container.

You can achieve this by implementing the following logic:

if (container.findIndex((item) => item.id === post.id) === -1) {
    container.push(new PostContainer(post, x[0].equippedItems));
}

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