Our next goal is to be able to save the edits we've made back to Strapi. We'll be doing this with a pretty simple GraphQL mutation.

First, since we're dealing with image uploading we'll need access to the CMS object again so that the Strapi media store can help us out.

pages/posts/[slug].js

- import { useForm, usePlugin } from "tinacms";
+ import { useCMS, useForm, usePlugin } from "tinacms";
  // ...

  export default function Post({ post: initialPost, morePosts, preview }) {
+   const cms = useCMS();
    // ...

Now we'll replace the dummy onSubmit that we created earlier with a function that calls a GraphQL mutation to when we submit the form.

pages/posts/[slug].js

    onSubmit: async (values) => {
      const saveMutation = `
      mutation UpdateBlogPost(
        $id: ID!
        $title: String
        $content: String
        $coverImageId: ID
      ) {
        updateBlogPost(
          input: {
            where: { id: $id }
            data: { title: $title, content: $content, coverImage: $coverImageId}
          }
        ) {
          blogPost {
            id
          }
        }
      }`;
      const response = await cms.api.strapi.fetchGraphql(
        saveMutation,
        {
          id: values.id,
          title: values.title,
          content: values.content,
          coverImageId: cms.media.store.getFileId(values.coverImage.url),
        }
      );
      if (response.data) {
        cms.alerts.success("Changes Saved");
      } else {
        cms.alerts.error("Error saving changes");
      }
    },

Take a read through the mutation, it's pretty simple! Strings prepended with a $ are variables that we send as a second argument to the fetchGraphql function. We're doing a little bit of magic with getFileId because we need to pass GraphQL the ID of the uploaded image and not the URL.

With this in place, reload your site and enter edit mode. Now make some changes to a blog post and click the save button. If everything has gone well, those changes will have been sent to Strapi and saved.