To Store Data In Materialized View

I have a PL/SQL procedure which gathers data from multiple places as well as calculates some data. I want to store all this in a materialized view.

So, I created an object type (I've shortened the definitions):

CREATE OR REPLACE TYPE mf_record_type AS OBJECT
(identifier VARCHAR2(6),
name VARCHAR2(100));

Then created the table type of the object:

CREATE OR REPLACE TYPE mf_table_type IS TABLE OF mf_record_type;

Then in the stored procedure defined a variable of the table type:

v_mf_record mf_table_type := mf_table_type();

Then I loop and populate the record type:

v_mf_record.EXTEND(1);
v_mf_record(x) := mf_record_type(v_rec.identifier, v_mf_detail.name);

When all that is done I try and create the materialized view:

EXECUTE IMMEDIATE ('CREATE MATERIALIZED VIEW mf_snapshot_mv AS
SELECT * FROM TABLE (CAST (v_mf_record AS mf_table_type))');

ORA-00904: "V_MF_RECORD": invalid identifier

Am I doing something wrong here? Can't I create the materialized view based on something other than a physical table?