14-MultipleLevelComponentCommunication.md

Lab 14: Component Communication through Multiple Levels

Objectives

• In a child component, accept a function as a prop and invoke it and pass a parameter
• At the next level in the component hierarchy, accept a function as a prop and invoke it
• In a parent component, implement a function and pass it as a prop to a child component

Steps

In a child component, accept a function as a prop and invoke it and pass a parameter

1. Open the file src\projects\ProjectForm.tsx.

2. On the ProjectFormProps interface, add an onSave function that requires a project as a parameter and returns void.

   src\projects\ProjectForm.tsx

   ...
   + import { Project } from './Project';
   
   interface ProjectFormProps {
   +  onSave: (project: Project) => void;
     onCancel: () => void;
   }
   ...

3. Create an event handler function handleSubmit to handle the submission of the form.

   The function should prevent the default behavior of the browser to post to the server and then invoke the function passed into the onSave prop and pass a new Project that you create inline for now with just a name as shown below.

   Update the <form> tag in the render method to invoke handleSubmit and pass the SyntheticEvent object representing the DOM submit event.

   src\projects\ProjectForm.tsx

   - function ProjectForm({ onSave, onCancel }: ProjectFormProps) {
   + function ProjectForm({ onCancel }: ProjectFormProps) {
   
   +  const handleSubmit = (event: SyntheticEvent) => {
   +    event.preventDefault();
   +    onSave(new Project({ name: 'Updated Project' }));
   +  };
   
   return (
   
      <form className="input-group vertical"
   +    onSubmit={handleSubmit}
      >
         <label htmlFor="name">Project Name</label>
         <input type="text" name="name" placeholder="enter name" />
         <label htmlFor="description">Project Description</label>
         <textarea name="description" placeholder="enter description" />
         <label htmlFor="budget">Project Budget</label>
         <input type="number" name="budget" placeholder="enter budget" />
         <label htmlFor="isActive">Active?</label>
         <input type="checkbox" name="isActive" />
         <div className="input-group">
         <button className="primary bordered medium">Save</button>
         <span />
         <button type="button" className="bordered medium" onClick={onCancel}>
            cancel
         </button>
         </div>
      </form>
   );
   }
   
   export default ProjectForm;

At the next level in the component hierarchy, accept a function as a prop and invoke it

1. Open the file src\projects\ProjectList.tsx.

2. On the ProjectListProps interface, add an onSave event handler that requies a project as a parameter and returns void.

   src\projects\ProjectList.tsx

   interface ProjectListProps {
     projects: Project[];
   + onSave: (project: Project) => void;
   }

3. Update the <ProjectForm> component tag to handle a onSave event and have it invoke the function passed into the onSave prop.

   src\projects\ProjectList.tsx

   interface ProjectListProps {
   projects: Project[];
   onSave: (project: Project) => void;
   }
   
   - function ProjectList({ projects }: ProjectListProps) {
   + function ProjectList({ projects, onSave }: ProjectListProps) {
   const [projectBeingEdited, setProjectBeingEdited] = useState({});
   
   const handleEdit = (project: Project) => {
      setProjectBeingEdited(project);
   };
   
   const cancelEditing = () => {
      setProjectBeingEdited({});
   };
   
   return (
      <div className="row">
         {projects.map((project) => (
         <div key={project.id} className="cols-sm">
            {project === projectBeingEdited ? (
               <ProjectForm
   +            onSave={onSave}
               onCancel={cancelEditing} />
            ) : (
               <ProjectCard project={project} onEdit={handleEdit} />
            )}
         </div>
         ))}
      </div>
   );
   }
   
   export default ProjectList;

In a parent component, implement a function and pass it as a prop to a child component

1. In the file src\projects\ProjectsPage.tsx:

   1. Add a saveProjectevent handler that takes a project to ProjectPage and console.log's the project out.
   2. Wire up the onSave event of the <ProjectList /> component rendered in the ProjectPage to the saveProject event handler.

   src\projects\ProjectsPage.tsx

   import React, { Fragment } from 'react';
   import { MOCK_PROJECTS } from './MockProjects';
   import ProjectList from './ProjectList';
   + import { Project } from './Project';
   
   function ProjectsPage() {
   +  const saveProject = (project: Project) => {
   +    console.log('Saving project: ', project);
   +  };
   
     return (
        <Fragment>
           <h1>Projects</h1>
           <ProjectList
   +         onSave={saveProject}
             projects={MOCK_PROJECTS} />
        </Fragment>
     );
   }
   
   export default ProjectsPage;

2. Verify the application is working by following these steps:

   1. Open the application in your browser and refresh the page.
   2. Open the Chrome DevTools to the console (F12 or fn+F12 on laptop).
   3. Click the edit button for a project.
   4. Click the save button on the form.
   5. Verify the updated project is logged to the Chrome DevTools console.

      Note that the ProjectCard info will not be updated at this point.

   

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✔ You have completed Lab 14