Mutation with newTask.id=responseData.id

[StokeMasterJack]

On line 77 in KanbanBoardContainer.addCard (chapter 5) you have:

newTask.id=responseData.id
this.setState({cards:nextState});

I noticed that you call setState with nextState before the ajax call. And you called setState with nextState after the ajax call. Isn't that mutating the deep state of nextState but returning the same pointer. In other words, why not use the "Immutability Helper update" method?

I thought that the whole reason for using "Immutability Helper update" was because you should't mutate the original object?

[cassiozen]

The setState is being called before the actual ajax call so the user can have de "feeling" that his/her action happened immediately. This is called "optimistic update".

Since we don't know the ID before the Ajax request, we simple use Date.now() as a temporary id.

After the actual Ajax call, it either updates this temporary, fake ID with the actual ID returned by the server OR (in case of error) revert the interface back to the previous state.

In all these moments, the component state is being treated as immutable. The local variables newTask and nextState are not - they are being mutated as the requests happen.

[StokeMasterJack]

Thanks

On Mon, Sep 19, 2016 at 2:06 PM, Cássio Souza notifications@github.com
wrote:

The setState is being called before the actual ajax call so the user can
have de "feeling" that his/her action happened immediately. This is called
"optimistic update".

Since we don't know the ID before the Ajax request, we simple use
Date.now() as a fake id.

After the actual Ajax call, it either updates this temporary, fake ID with
the actual ID returned by the user OR (in case of error) revert the
interface back to the previous state.

In all these moments, the component state is being treated as immutable.
The local variables newTask and nextState are not - they are being mutated
as the requests happen.

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