How could i access different view controls by sap.ui.getCore().byId() ? it doesn't work it shows an error

I cannot access elements via byId() from different view/controller.

I am trying to access another view elements by using below  syntax.

sap.ui.getCore().byId("xxx").setModel(oModel2);

But it shows error like (Cannot read property 'setModel' of undefined).

I found some answ in SCN blog they said that

When you do createID('XY'), the element is created with an ID havinbg format <prefix>XY . The prefix is that of the view. So when you do sap.ui.getCore().byId('XY'), you will not find any element with ID 'XY'.

Please help me. How could i achieve.