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I've been doing most of my projects lately with React and enigma.js, and developing some general patterns along the way that I've been working into a starter project that I can use as a starting point. I'd like to share that with you today, and potentially start a discussion around the design decisions I've made thus far.
The starter project can be found at GitHub - fkabinoff/qlik-react-starter: Starter project for rapidly developing QAP-powered apps. It's still very much in development, but there's a decent framework and dev environment in place, as well as a few useful components.
Overview
The project uses enigma.js to interface with the Qlik engine, along with React, webpack, Babel, ESLint, Sass, and a few other goodies. Really, a pretty standard React app with enigma.js added. The qDoc, which is the name the enigma.js docs use for the connection to the Qlik app is created in a plain Javascript module and simply imported to any file that needs to use it.
I use react-hot-loader, which allows you to change react components without refreshing the page or losing state, and I really like it. It has it's problems, most noticeably to me that it doesn't play very nicely with higher order components, but the ability to change my React components and not have to reload the page or lose state helps me develop faster.
I'm using the latest Babel preset, which enables es2015, es2016, and es2017, and Babel plugins which enable decorators, spread syntax, and class properties. I can't believe we actually wrote Javascript before this stuff.
I use the very popular airbnb config for ESLint. It helps keep the code healthy and uniform.
I make use of reactstrap, a library of Bootstrap 4 components for React, and SASS for customizing and mixing in Bootstrap styles, as well as creating a few utility classes. I prefer using reactstrap over some of the more feature-rich React UI libraries, because I often find it creates more work trying to make the components of those UI libraries, such as Material UI, play nicely with how I want a component in a Qlik-powered app to function since in a Qlik-powered app the Qlik engine acts as a state machine, and many of the UI libraries with more features expect the state to be managed and changed by the client. Reactstrap gives me what I need, without being too opinionated about it.
I use the "render prop" pattern in place of higher order components. The render prop pattern is simply passing a component as a prop to another component for that component to render it. It basically works like a higher order component does, but to me it's a bit simpler, a little more flexible, and doesn't mess with react-hot-reload or PropTypes checking.
Notably, I don't use a state manager like Redux or MobX, and this may be my most contentious decision. To me, the use of a state manager in most instances is redundant when building a Qlik-powered app. Qlik already manages my state, and shares it between components. I hardly, if ever, have state that needs to be managed outside of Qlik in my Qlik-powered apps, and using a state manager forces me to do extra work to keep the client state and Qlik state in sync. I don't like it.
It would be very interesting to hear what you think about these design decisions, and the decisions that you've made with your own Qlik projects.
Components
Now, let's take a look at the actual components. There are currently 4 Qlik-specific components, but I expect to add more as I continue developing this. I tried to design the Qlik-specific components to expect props which are identical to values defined in Qlik docs, and pass down values directly returned by the Qlik engine, in order to standardize as much as possible. Though in some instances, I broke that rule. For instance, since the QlikObject wrapper, which I'll talk about in a moment, is really only designed to work with an object that fetches one page, it didnt make sense to pass down the qDataPages returned by the Qlik generic object getData method. Instead, I simply pass down the object at the first index of qDataPages.
QlikObject.jsx
The QlikObject component implements the render prop pattern, and contains the logic to create and manage a Qlik generic object and its state. It passes down the Qlik generic object information to the component defined in the Component prop, which is responsible for rendering something.
QlikVirtualScroll.jsx
The QlikVirtualScroll component implements the render prop pattern, and paginates data on vertical scroll so only data in view gets rendered. It passes down a subet of the qMatrix to the component defined in the Component prop, which is responsible for rendering something. It is used by the QlikFilter and QlikTable components.
QlikFilter.jsx
The QlikFilter component renders a dropdown that acts as a Qlik Sense filter. It's meant to be used as the `Component` prop of a `QlikObject` component a type of `qListObject`. This component doesn't need to be passed any props other than the props passed to it by `QlikObject`.
QlikTable.jsx
The QlikTable component renders a table. It's meant to be used as the `Component` prop of a `QlikObject` component with a type of `qHyperCube`. This component requires a prop `columnWidths` to be passed to it, defining the widths of the columns of the table. This prop should be passed using the `componentProps` prop of the `QlikObject`.
Finishing up
Go to GitHub - fkabinoff/qlik-react-starter: Starter project for rapidly developing QAP-powered apps, download the zip, run npm install, and npm run dev, and you can check out the QlikFilter and QlikTable components in action, and check out the code. I'll be adding more components and styles as I'm still pretty actively developing it, so watch the repo if you're interested, and let me know what you think.
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