Wireshark lua scripting to dissect CoAP option

I'm writing lua script to dissect coap protocol. However I cannnot get coap options(URI-Path) of 2nd or later if there are several same options.

do
 local test_proto = Proto("test_proto", "Test Protocol")
 local test_uripath = ProtoField.string("test.uripath", "Uri-Path")
 test_proto.fields = {test_uripath}
 local coap_uripath = Field.new("coap.opt.uri_path")
 function test_proto.dissector(tvbuffer, pinfo, treeitem)
  local subtree = treeitem:add(test_proto)
  subtree:add(test_uripath, tostring(coap_uripath().value))
 end
register_postdissector(test_proto)
end

Only first URI-Path is displayed at subtree even if coap URI-Path option has several values like the following.

Opt Name: #1: URI-Path: XXX
Opt Name: #2: URI-Path: YYY

I can only get XXX by using coap.opt.uri_path. How can I get 2nd or later same option fields?

Solution

If you're interested in all fields and not just the first one, then you'll need to process the entire table. For example:

do
    local test_proto = Proto("test_proto", "Test Protocol")
    local test_uripath = ProtoField.string("test.uripath", "Uri-Path")
    test_proto.fields = {test_uripath}

    local coap_uripath = Field.new("coap.opt.uri_path")

    function test_proto.dissector(tvbuffer, pinfo, treeitem)
        local subtree = treeitem:add(test_proto)
        local coap_uripath_table = { coap_uripath() }

        for i,uripath in ipairs(coap_uripath_table) do
            subtree:add(test_uripath, tostring(uripath.value))
        end
    end

    register_postdissector(test_proto)
end