No more session abuse
January 2, 2016

In a typical example of having 2 grids that handle models bound with a one-to-many relationship, we used to need an endpoint that would receive the id of the currently selected parent record and store it in the session, so that the next endpoint call that is processed by the second grid would already have that grid reconfigured for us, scoping it out to the record selected. It usually looked something like this:

endpoint :server_set_author do |params, this|
  # store author_id in the session:
  component_session[:current_author_id] = params[:author_id]
end

component :books do |c|
  # filter books data by author id stored in the session:
  c.scope = {author_id: component_session[:current_author_id]}
end

Then on the client we would do something like this:

this.netzkeGetComponent('authors').on('rowclick', function(grid, record) {
  // call the "server_update_author" endpoint of the server side
  this.serverSetAuthor({author_id: record.getId()});

  // inform the client-side of the Books grid to reload itself
  this.netzkeGetComponent('books').getStore().load();
}, this);

Given we could have dozens of configurations like this, this was very heavy on the session, which resulted in session size exceeded very quickly, and the remedy for that would be to use the database to store the session. Not very performant a solution, and besides it didn’t feel clean. Now there’s a better way.

Currently Netzke implements a way to reconfigure any instantiated component directly from the client side by using special serverConfig property. Whatever is stored in that object is passed along with every endpoint call and is accessible on the server side via client_config method. So, on the client we can now do this:

this.netzkeGetComponent('authors').on('rowclick', function(grid, record) {
  // configure our top component with the new current_author_id
  this.serverConfig['current_author_id'] = record.getId();

  // inform the client-side of the Books grid to reload itself
  this.netzkeGetComponent('books').getStore().load();
}, this);

No more call to the server_set_author endpoint, so, we can get rid of it. And the books grid can be configured like this now:

component :books do |c|
  # filter books data by author id passed from the client
  c.scope = {author_id: client_config[:current_author_id]}
end

I updated the “Bosses and Clerks” example in the official demo to use this technique, too.

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