add update

addupdate.ts

ADD_COURSE,
{
  update (cache, { data }) {
    const newCourseFromResponse = data?.addCourse.course;
    const existingCourses = cache.readQuery<GetAllCourses>({
      query: GET_ALL_COURSES,
    });

    if (existingCourses && newCourseFromResponse) {
      cache.writeQuery({
        query: GET_ALL_COURSES,
        data: {
          toCourses: [
            ...existingCourses?.courses,
            newCourseFromResponse,
          ],
        },
      });
    }
  }