[table] Allow columns to be hidden

Bug, feature request, or proposal:

Feature request

What is the expected behavior?

It would be nice to change cdkColumnDef to null or undefined programmatically to remove the column from the table

What is the current behavior?

Nothing occurs when you change the mat-header or mat-cell in mat-table.

What are the steps to reproduce?

https://stackblitz.com/edit/material2-hide-columns

What is the use-case or motivation for changing an existing behavior?

This would allow me to write a generalized component for hiding sections of the datatable for certain screen sizes, allowing mobile data-tables to be better

[crutchcorn]

I’m incredibly dumb. Thank you @benb7760

[benb7760]

@crutchcorn your class variable displayColumns is only set when you are initialising the class, and not getting updated when you call test. You could either update your test method to update displayedColumns or you could change it to a get accessor

get displayedColumns() { return this.columns.map(c => c.columnDef); }