Help needed on dynamic case-whens

[adithyagenie]

I'm trying to do a dynamic case-when, where I add when clauses in a loop.

let mut data: Vec<i32> = HashMap<i32, i32> = HashMap::new();
data.insert(1000, 1);
data.insert(2000, 2);
data.insert(3000, 3);
let mut update_query = case_when(id.eq(1), data.get(&1000)).when(id.eq(2), data.get(&2000));
// for the sql query
// CASE
//     WHEN id = 1 THEN count + data.get(&1000)
//     WHEN id = 2 THEN count + data.get(&2000)
// END

How do I do this over a for loop? I tried something like

let mut update_query;
for (item, count) in freq_map {
    if (update_query == None) {
        update_query = case_when(item_id.eq(item), num + count);
    }
    else {
        update_query = update_query.when(item_id.eq(item), num + count);
    }
}

and I get type errors. Can someone please help me out on this?

[weiznich]

This is currently expected behavior as each call of .when() returns a different type, so you cannot reassign the value to the same variable. We are open to accept a PR that adds a variant of that operator that does not have this constraint.