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Component lifecycle

To see how component is handled by Drayman, let's take for example, a component which reads data from selected file and shows it to user:

import fs from "fs/promises";
export const component: DraymanComponent = async ({  forceUpdate,  ComponentInstance,}) => {  ComponentInstance.onDestroy = () => {    console.log(`Component instance was destroyed!`);  };
  const files = ["", ...(await fs.readdir("."))];  let selectedFileContent: string;
  return async () => {    return (      <>        <select          onchange={async ({ value }) => {            selectedFileContent = await fs.readFile(value, "utf-8");            await forceUpdate();          }}        >          { => (            <option value={fileName}>{fileName}</option>          ))}        </select>        <br />        {selectedFileContent && <pre>{selectedFileContent}</pre>}      </>    );  };};

When user visits a page with this component here is what happens:

  • A module.execute function gets called with helper objects and returned function gets stored. Let's call this returned function a render function.
  • A data returned by render function is what user actually sees on the page. This function, in turn, gets called each time a forceUpdate function gets called (you can read about forceUpdate in detail here). To show initial result to user, forceUpdate is executed and user's browser receives instructions of what should be rendered on page.
  • Next steps of component lifecycle are decided by user.
    • If user selects some option, an onchange event gets triggered on select element. In our component this event reads file contents and calls forceUpdate function. As described before, forceUpdate function calls render function behind the scenes and user receives a new representation of component.
    • If user decides to close a page with component or component disappears from DOM, onDestroy method of the ComponentInstance gets called printing Component instance was destroyed! message to the console and component instance with render function gets destroyed.