ExtJs4 - What is the equivalent to the grid ColumnModel?

Question

What is the equivalent to the ExtJs3 Ext.grid.ColumnModel in ExtJs4?

What I want to do is hide a column, I did something like below in ExtJs3:

Answer 1

Another solution more flexible :

grid.down("[dataIndex="+di+"]").setVisible(v);

You can change dataIndex for another property like name or whatever.