Cell builder plugin

Read slowly and carefully! The concept is simple, yet the interface is strict.

Start Here

  • A plugin of type cell_styles does nothing except getting a configuration and returning a rendering function that accepts two props: item and state.
  • The returning function is used to render a cell in a component.

Plugin Interface / Signature

Module Root

  • The exported index.js must be a function that gets a configuration object:
// index.js
import { Foo } from "./src";
const FooPlugin = (configuration) => Foo(configuration);
module.exports = FooPlugin;

Returned Function

  • The returned function must accept two props item and state
  • Simplified example: a function that returns two <Text/> nodes showing the title of the item and the state
// src/Foo.js
import * as React from "react";
import { View, Text } from "react-native";
export function Foo(configuration) {
// doing something with the configuration object...
return function RenderFoo({ item, state }) {
return (
<Text>Title: { item.title }</Text>
<Text>State: { state }</Text>

Objects and Props in-depth


type Configuration = {
component: { // component configuration, as-is, from rivers.json
component_type: string // the most useful property
styles: any, // styles.json via redux store
cellStyles: any // cell_styles.json via redux store
  • Reference - component object
  • styles is 100% identical to styles configuration of the app version in Zapp, visible in app version > info > reveal build parameters > styles_url
  • The styles data can be used effectivly to provide common styling across the various cell styles, like app background color, or main text color. Please refer to the examples below.
  • cellStyles is the combined configuration of all of the cell styles that were created for the layout in the Cell Styles Builder tab in the Ui Builder
  • Reference - cell_styles.json structure


type item = {
id: string,
title: string,
type: {
value: string
media_group: [
media_item: [
src: string,
key: string,
type: string,
... // many more optional properties!
  • Reference: feed item schema
  • The item parameter is actually a an entry, taken straight from the feed assigned to the Ui Component.
  • The item will always have an id and a title, but all the other fields could be optional / missing.
  • Please refer to current built-in cell styles plugins in this repo to get an idea of how data is retrieved from an item object.
  • IMPORTANT : It is the plugin's total responsability to dig into the media_group and media_item objects in order to retrieve thumbnail images, video files etc.
  • It is a good practice for a plugin to provide decent fallbacks for missing fields, e.g. placeholder for missing thumbnail image(s).


type state =
| "default"
| "selected"
| "focused";
| undefined
  • The state string represent the abstract "ui state" of the cell. Fallback is always to "default"
  • Common examples for states:
    • "selected": mark some "current item" in a screen picker
    • "selected": give a feedback for the user when he taps the cell
    • "focused": highlight current focused cell in a TV app
  • TAKE CARE : Each platform deals with states in a different way - e.g. TV apps makes extensive use of compound "focused" states, while mobile apps use that state only to give some sensory feedback to a selection. YMMV!

Real Life Examples

Demo Cell Builder Plugin

  • code
  • This is a rather complex example, but worth looking into
  • This plugin checks for the component_type property of the component, and returns matching styles / view trees / configuration for each component type.
  • This plugin extracts the matching configuration for the cell style, and uses the masterCellBuilder to create trees for each UI state.
  • This plugin uses both the global styles from Zapp and the individual configuration of a cell style to draw cells:
    • Since text color is taken from the global styles, it is consistent with the whole app
    • The backround color, on the other hand, is taken from the plugin configuration - where we can fine-tune a specific color for the "default" and "focused" states.

Quick Brick Master Cell

  • code
  • This plugin exhibits a complex configuration, all found in the plugin's manifest
  • Except a few hard-coded constants, almost any visual aspect of the resulting cell is to be controlled from the configuration panel, including positioning of elements.