Lab 26: Custom Hooks

This lab is optional and should only be done if time permits

Objectives

• Move stateful logic out of components by creating Custom Hooks

Steps

1. This lab is a refactor of the code from the solution of lab22 so begin by checking out the lab22 solution code and creating a working branch for this lab.

   git checkout lab22
   git checkout -b lab26working

2. Create a projectHooks.ts file and add the following code.

   src\projects\projectHooks.ts

   import { useState, useEffect } from 'react';
   import { projectAPI } from './projectAPI';
   import { Project } from './Project';
   
   export function useProjects() {
     const [projects, setProjects] = useState<Project[]>([]);
     const [loading, setLoading] = useState(false);
     const [error, setError] = useState<string | undefined>(undefined);
     const [currentPage, setCurrentPage] = useState(1);
     const [saving, setSaving] = useState(false);
     const [savingError, setSavingError] = useState<string | undefined>(
       undefined
     );
   
     useEffect(() => {
       async function loadProjects() {
         setLoading(true);
         try {
           const data = await projectAPI.get(currentPage);
           if (currentPage === 1) {
             setProjects(data);
           } else {
             setProjects((projects) => [...projects, ...data]);
           }
         } catch (e) {
           if (e instanceof Error) {
             setError(e.message);
           }
         } finally {
           setLoading(false);
         }
       }
       loadProjects();
     }, [currentPage]);
   
     const saveProject = (project: Project) => {
       setSaving(true);
       projectAPI
         .put(project)
         .then((updatedProject) => {
           let updatedProjects = projects.map((p) => {
             return p.id === project.id ? new Project(updatedProject) : p;
           });
           setProjects(updatedProjects);
         })
         .catch((e) => {
           setSavingError(e.message);
         })
         .finally(() => setSaving(false));
     };
   
     return {
       projects,
       loading,
       error,
       currentPage,
       setCurrentPage,
       saving,
       savingError,
       saveProject,
     };
   }

   Notice how this logic was directly lifted out of the ProjectsPage component.

3. Refactor the ProjectsPage component to remove the logic which is now in the hook and call the hook instead.

Be sure to open the ProjectsPage.tsx and not the singular ProjectPage.tsx

src\projects\ProjectsPage.ts

-import React, { useState, useEffect } from 'react';
+import React from 'react';
 import ProjectList from './ProjectList';
-import { projectAPI } from './projectAPI';
-import { Project } from './Project';
+import { useProjects } from './projectHooks';

function ProjectsPage() {
-  const [projects, setProjects] = useState<Project[]>([]);
-  const [loading, setLoading] = useState(false);
-  const [error, setError] = useState<string | undefined>(undefined);
-  const [currentPage, setCurrentPage] = useState(1);
-  const [saving, setSaving] = useState(false);
-  const [savingError, setSavingError] = useState<string | undefined>(undefined);




-  useEffect(() => {
-    async function loadProjects() {
-      setLoading(true);
-      try {
-        const data = await projectAPI.get(currentPage);
-        if (currentPage === 1) {
-          setProjects(data);
-        } else {
-          setProjects((projects) => [...projects, ...data]);
-        }
-      } catch (e) {
-         if (e instanceof Error) {
-          setError(e.message);
-        }
-      } finally {
-        setLoading(false);
-      }
-    }
-    loadProjects();
-  }, [currentPage]);

+  const {
+    projects,
+    loading,
+    error,
+    setCurrentPage,
+    saveProject,
+    saving,
+    savingError,
+  } = useProjects();

   const handleMoreClick = () => {
     setCurrentPage((currentPage) => currentPage + 1);
   };

-  const saveProject = (project: Project) => {
-    projectAPI
-      .put(project)
-      .then((updatedProject) => {
-        let updatedProjects = projects.map((p) => {
-          return p.id === project.id ? new Project(updatedProject) : p;
-        });
-        setProjects(updatedProjects);
-      })
-      .catch((e) => {
-        if (e instanceof Error) {
-          setError(e.message);
-        }
-      });
-  };

   return (
     <>
       <h1>Projects</h1>
+      {saving && <span className="toast">Saving...</span>}

-      {error && (
+      {(error || savingError) && (
         <div className="row">
           <div className="card large error">
             <section>
               <p>
                 <span className="icon-alert inverse "></span>
-                {error}
+                {error} {savingError}
               </p>
             </section>
           </div>
         </div>
    </>
  );
}

export default ProjectsPage;

4. Test the application to verify the loading, saving and error messages are displaying.

   • Add this line to test the loading spinner

     src\projects\projectAPI.ts

       get(page = 1, limit = 20) {
         return fetch(`${url}?_page=${page}&_limit=${limit}&_sort=name`)
     +     .then(delay(2000))
           .then(checkStatus)
           .then(parseJSON)
           .catch((error: TypeError) => {
             console.log('log client error ' + error);
             throw new Error(
               'There was an error retrieving the projects. Please try again.'
             );
           });
       },
     • Shut down your backend API to test the display of an error message

✔ You have completed Lab 26