# Processing YAML in Lua You may need to deal with YAML data in your Lua code. ## root/usr/libexec/rpcd/luci.example These are the changes you would need in the `usr/libexec/rpcd/luci.example` file. First, declare that you want YAML libraries: ```lua -- If you need to process YAML, opkg install lyaml local lyaml = require "lyaml" ``` Then, declare a function to handle the YAML data, and a helper to read the file ```lua local function readfile(path) local s = fs.readfile(path) return s and (s:gsub("^%s+", ""):gsub("%s+$", "")) end local function reading_from_yaml() -- Use the locally declared readfile() function to read in the -- sample YAML file that ships with this package. local example_config = readfile("/etc/luci.example.yaml") -- Map that string to a Lua table via lyaml's load() method local example_table = lyaml.load(example_config) -- Convert the table to JSON local example_json = jsonc.stringify(example_table) -- Pass the JSON back return example_json end ``` Declare the method in the `methods` table ```lua -- Converts the AGH YAML configuration into JSON for consumption by -- the LuCI app. get_yaml_file_sample = { -- A special key of 'call' points to a function definition for execution. call = function() local r = {} r.result = reading_from_yaml() -- The 'call' handler will refer to '.code', but also defaults if not found. r.code = 0 -- Return the table object; the call handler will access the attributes -- of the table. return r end }, ``` ## htdocs/luci-static/resources/view/example/rpc.js These are the changes you need in the `rpc.js` file. Declare the RPC call ```js const load_sample_yaml = rpc.declare({ object: 'luci.example', method: 'get_yaml_file_sample' }); ``` Add this declaration to the `view.extend()` call ```js render_sample_yaml: function(sample) { console.log('render_sample_yaml()'); console.log(sample); if (sample.error) { return this.generic_failure(sample.error) } // Basically, a fully static table declaration. var table = E('table', { 'class': 'table', 'id': 'sample-yaml' }, [ E('tr', {}, [ E('td', { 'class': 'td left', 'width': '33%' }, _("Top Level Int")), E('td', { 'class': 'td left' }, sample.top_level_int), ]), E('tr', {}, [ E('td', { 'class': 'td left', 'width': '33%' }, _("Top Level String")), E('td', { 'class': 'td left' }, sample.top_level_string), ]) ]); return table; }, ``` Add a call to the `load` function in `view.extend()` ```js load: function () { return Promise.all([ load_sample_yaml(), load_sample1() ]); }, ``` Add this code to the `render` function in `view.extend()` ```js E('div', { 'class': 'cbi-section', 'id': 'cbi-sample-yaml' }, [ E('div', { 'class': 'left' }, [ E('h3', _('Sample YAML via RPC')), E('div', {}), _("YAML transformed to JSON, table built explicitly"), this.render_sample_yaml(sample_yaml), ]), ]), ``` ## root/usr/share/rpcd/acl.d/luci-app-example.json Allow access to the new RPC API ```json "read": { "ubus": { "luci.example": [ "get_yaml_file_sample", "get_sample1", "get_sample2" ] }, ``` ## root/etc/luci.example.yaml Set up the sample YAML file, by placing it either in `root/etc` of the development tree, or directly in `/etc` on the target machine and call it `luci.example.yaml` to match up to the `reading_from_yaml` function's expectations. ```yaml top_level_string: example top_level_int: 8080 top_level: list_elements: - foo - bar ``` That's it. Don't forget to also update the `LUCI_DEPENDS` segment of the `Makefile` to include `+lyaml` so that the packaging system knows your code needs the YAML parsing package.