How to use declared variable to create a json element - json

Question

I have a stored procedure, in this, I have declared a variable which holds a value from a select function. I need to use this value to create a json element, but it throws an exception
function jsonb_set(jsonb, unknown, character varying, boolean) does not exist
This is the function:
CREATE OR REPLACE FUNCTION test ( ) RETURNS
INTEGER AS $$
DECLARE
intent varchar;
BEGIN
select id into intent from customer;
UPDATE orders
SET data = jsonb_set(
data,
'{Items}', -- the array in which we operate
to_jsonb(
(WITH ar AS(
WITH temp AS(
SELECT data->'Items' AS items -- the array in which we operate
FROM orders
WHERE id = 1 -- the filtered order we are updating
)
SELECT jsonb_set(
jsonb_array_elements(items),
'{Quantity}', -- the new field we are adding
intent, -- this is where i need to replace the variable
true)
FROM temp)
SELECT (array_agg(ar.jsonb_set))
FROM ar)),
false)
WHERE id = 1;
return 0;
EXCEPTION WHEN others THEN
return 1;
END;
$$ LANGUAGE plpgsql;
Copying the snippet where I need to replace the variable:
SELECT jsonb_set(
jsonb_array_elements(items),
'{Quantity}', -- the new field we are adding
intent, -- this is where i need to replace the variable
true)

Answer 1

You have to explicitly cast intent to jsonb using CAST(intent AS jsonb) or intent::jsonb.
The reason it works with a string literal is that such literals are of the (internal) type unknown which can be transformed to most other types, but there is no implicit cast between character varying and jsonb, so you have to use an explicit one.