SSAS - Calculation in DSV or in view from data source
Adding calculations either in DSV or in a view do not have much difference, it is just a choice, where you wish to maintain your SQL code. You can take a decision based on, which approach is best suited for you, from maintenance point of view.

following link can be helpful: 
https://social.msdn.microsoft.com/Forums/sqlserver/en-US/42215fd0-9cc4-4463-b739-de116f1d38be/named-calculations-vs-calculated-members?forum=sqlanalysisservices