@rikishi/watermelondb
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Build powerful React Native and React web apps that scale from hundreds to tens of thousands of records and remain fast
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<ol class="chapter"><li class="chapter-item expanded "><a href="ch01-00-get-excited.html"><strong aria-hidden="true">1.</strong> Get excited</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="index.html"><strong aria-hidden="true">1.1.</strong> Check out the README</a></li><li class="chapter-item expanded "><a href="Demo.html"><strong aria-hidden="true">1.2.</strong> See the demo</a></li></ol></li><li class="chapter-item expanded "><a href="ch02-00-learn-to-use.html"><strong aria-hidden="true">2.</strong> Learn to use Watermelon</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="Installation.html"><strong aria-hidden="true">2.1.</strong> Installation</a></li><li class="chapter-item expanded "><a href="Setup.html"><strong aria-hidden="true">2.2.</strong> Setup</a></li><li class="chapter-item expanded "><a href="Schema.html"><strong aria-hidden="true">2.3.</strong> Schema</a></li><li class="chapter-item expanded "><a href="Model.html"><strong aria-hidden="true">2.4.</strong> Defining Models</a></li><li class="chapter-item expanded "><a href="CRUD.html" class="active"><strong aria-hidden="true">2.5.</strong> Create, Read, Update, Delete</a></li><li class="chapter-item expanded "><a href="Components.html"><strong aria-hidden="true">2.6.</strong> Connecting to React Components</a></li><li class="chapter-item expanded "><a href="Query.html"><strong aria-hidden="true">2.7.</strong> Querying</a></li><li class="chapter-item expanded "><a href="Relation.html"><strong aria-hidden="true">2.8.</strong> Relations</a></li><li class="chapter-item expanded "><a href="Writers.html"><strong aria-hidden="true">2.9.</strong> Writers, Readers, batching</a></li></ol></li><li class="chapter-item expanded "><a href="ch03-00-advanced.html"><strong aria-hidden="true">3.</strong> Advanced guides</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="Advanced/Migrations.html"><strong aria-hidden="true">3.1.</strong> Migrations</a></li><li class="chapter-item expanded "><a href="Advanced/Sync.html"><strong aria-hidden="true">3.2.</strong> Sync</a></li><li class="chapter-item expanded "><a href="Advanced/CreateUpdateTracking.html"><strong aria-hidden="true">3.3.</strong> Automatic create/update tracking</a></li><li class="chapter-item expanded "><a href="Advanced/AdvancedFields.html"><strong aria-hidden="true">3.4.</strong> Advanced fields</a></li><li class="chapter-item expanded "><a href="Advanced/Flow.html"><strong aria-hidden="true">3.5.</strong> Flow</a></li><li class="chapter-item expanded "><a href="Advanced/LocalStorage.html"><strong aria-hidden="true">3.6.</strong> LocalStorage</a></li><li class="chapter-item expanded "><a href="Advanced/ProTips.html"><strong aria-hidden="true">3.7.</strong> Pro tips</a></li><li class="chapter-item expanded "><a href="Advanced/Performance.html"><strong aria-hidden="true">3.8.</strong> Performance tips</a></li><li class="chapter-item expanded "><a href="Advanced/SharingDatabaseAcrossTargets.html"><strong aria-hidden="true">3.9.</strong> iOS - Sharing database across targets</a></li></ol></li><li class="chapter-item expanded "><a href="ch04-00-deeper.html"><strong aria-hidden="true">4.</strong> Dig deeper into WatermelonDB</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="Implementation/Architecture.html"><strong aria-hidden="true">4.1.</strong> Architecture</a></li><li class="chapter-item expanded "><a href="Implementation/Adapters.html"><strong aria-hidden="true">4.2.</strong> Adapters</a></li><li class="chapter-item expanded "><a href="Implementation/SyncImpl.html"><strong aria-hidden="true">4.3.</strong> Sync implementation</a></li></ol></li><li class="chapter-item expanded "><a href="ch04-00-deeper.html"><strong aria-hidden="true">5.</strong> Other</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="Roadmap.html"><strong aria-hidden="true">5.1.</strong> Roadmap</a></li><li class="chapter-item expanded "><a href="CONTRIBUTING.html"><strong aria-hidden="true">5.2.</strong> Contributing</a></li><li class="chapter-item expanded "><a href="CHANGELOG.html"><strong aria-hidden="true">5.3.</strong> Changelog</a></li></ol></li></ol>
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<h1 id="create-read-update-delete"><a class="header" href="#create-read-update-delete">Create, Read, Update, Delete</a></h1>
<p>When you have your <a href="./Schema.html">Schema</a> and <a href="./Model.html">Models</a> defined, learn how to manipulate them!</p>
<h2 id="reading"><a class="header" href="#reading">Reading</a></h2>
<h4 id="get-a-collection"><a class="header" href="#get-a-collection">Get a collection</a></h4>
<p>The <code>Collection</code> object is how you find, query, and create new records of a given type.</p>
<pre><code class="language-js">const postsCollection = database.get('posts')
</code></pre>
<p>Pass the <a href="./Schema.html">table name</a> as the argument.</p>
<h4 id="find-a-record-by-id"><a class="header" href="#find-a-record-by-id">Find a record (by ID)</a></h4>
<pre><code class="language-js">const postId = 'abcdefgh'
const post = await database.get('posts').find(postId)
</code></pre>
<p><code>find()</code> returns a Promise. If the record cannot be found, the Promise will be rejected.</p>
<h4 id="query-records"><a class="header" href="#query-records">Query records</a></h4>
<p>Find a list of records matching given conditions by making a Query and then fetching it:</p>
<pre><code class="language-js">const allPosts = await database.get('posts').query().fetch()
const numberOfStarredPosts = await database.get('posts').query(
Q.where('is_starred', true)
).fetchCount()
</code></pre>
<p><strong>➡️ Learn more:</strong> <a href="./Query.html">Queries</a></p>
<h2 id="modifying-the-database"><a class="header" href="#modifying-the-database">Modifying the database</a></h2>
<p>All modifications to the database (like creating, updating, deleting records) must be done <strong>in a Writer</strong>, either by wrapping your work in <code>database.write()</code>:</p>
<pre><code class="language-js">await database.write(async () => {
const comment = await database.get('comments').find(commentId)
await comment.update(() => {
comment.isSpam = true
})
})
</code></pre>
<p>Or by defining a <code>@writer</code> method on a Model:</p>
<pre><code class="language-js">import { writer } from '@rikishi/watermelondb/decorators'
class Comment extends Model {
// (...)
@writer async markAsSpam() {
await this.update(comment => {
comment.isSpam = true
})
}
}
</code></pre>
<p><strong>➡️ Learn more:</strong> <a href="./Writers.html">Writers</a></p>
<h3 id="create-a-new-record"><a class="header" href="#create-a-new-record">Create a new record</a></h3>
<pre><code class="language-js">const newPost = await database.get('posts').create(post => {
post.title = 'New post'
post.body = 'Lorem ipsum...'
})
</code></pre>
<p><code>.create()</code> takes a "builder function". In the example above, the builder will get a <code>Post</code> object as an argument. Use this object to set values for <a href="./Model.html">fields you defined</a>.</p>
<p><strong>Note:</strong> Always <code>await</code> the Promise returned by <code>create</code> before you access the created record.</p>
<p><strong>Note:</strong> You can only set fields inside <code>create()</code> or <code>update()</code> builder functions.</p>
<h3 id="update-a-record"><a class="header" href="#update-a-record">Update a record</a></h3>
<pre><code class="language-js">await somePost.update(post => {
post.title = 'Updated title'
})
</code></pre>
<p>Like creating, updating takes a builder function, where you can use field setters.</p>
<p><strong>Note:</strong> Always <code>await</code> the Promise returned by <code>update</code> before you access the modified record.</p>
<h3 id="delete-a-record"><a class="header" href="#delete-a-record">Delete a record</a></h3>
<p>There are two ways of deleting records: syncable (mark as deleted), and permanent.</p>
<p>If you only use Watermelon as a local database, destroy records permanently, if you <a href="./Advanced/Sync.html">synchronize</a>, mark as deleted instead.</p>
<pre><code class="language-js">await somePost.markAsDeleted() // syncable
await somePost.destroyPermanently() // permanent
</code></pre>
<p><strong>Note:</strong> Do not access, update, or observe records after they're deleted.</p>
<h2 id="advanced"><a class="header" href="#advanced">Advanced</a></h2>
<ul>
<li><code>Model.observe()</code> - usually you only use this <a href="./Components.html">when connecting records to components</a>, but you can manually observe a record outside of React components. The returned <a href="https://github.com/reactivex/rxjs">RxJS</a> <code>Observable</code> will emit the record immediately upon subscription, and then every time the record is updated. If the record is deleted, the Observable will complete.</li>
<li><code>Query.observe()</code>, <code>Relation.observe()</code> — analagous to the above, but for <a href="./Query.html">Queries</a> and <a href="./Relation.html">Relations</a></li>
<li><code>Query.observeWithColumns()</code> - used for <a href="./Components.html">sorted lists</a></li>
<li><code>Collection.findAndObserve(id)</code> — same as using <code>.find(id)</code> and then calling <code>record.observe()</code></li>
<li><code>Model.prepareUpdate()</code>, <code>Collection.prepareCreate</code>, <code>Database.batch</code> — used for <a href="./Writers.html">batch updates</a></li>
<li><code>Database.unsafeResetDatabase()</code> destroys the whole database - <a href="https://github.com/Nozbe/WatermelonDB/blob/22188ee5b6e3af08e48e8af52d14e0d90db72925/src/Database/index.js#L131">be sure to see this comment before using it</a></li>
<li>To override the <code>record.id</code> during the creation, e.g. to sync with a remote database, you can do it by <code>record._raw</code> property. Be aware that the <code>id</code> must be of type <code>string</code>.
<pre><code class="language-js">await database.get('posts').create(post => {
post._raw.id = serverId
})
</code></pre>
</li>
</ul>
<h3 id="advanced-unsafe-raw-execute"><a class="header" href="#advanced-unsafe-raw-execute">Advanced: Unsafe raw execute</a></h3>
<p>⚠️ Do not use this if you don't know what you're doing...</p>
<p>There is an escape hatch to drop down from WatermelonDB to underlying database level to execute arbitrary commands. Use as a last resort tool:</p>
<pre><code class="language-js">await database.write(() => {
// sqlite:
await database.adapter.unsafeExecute({
sqls: [
// [sql_query, [placeholder arguments, ...]]
['create table temporary_test (id, foo, bar)', []],
['insert into temporary_test (id, foo, bar) values (?, ?, ?)', ['t1', true, 3.14]],
]
})
// lokijs:
await database.adapter.unsafeExecute({
loki: loki => {
loki.addCollection('temporary_test', { unique: ['id'], indices: [], disableMeta: true })
loki.getCollection('temporary_test').insert({ id: 't1', foo: true, bar: 3.14 })
}
})
})
</code></pre>
<hr />
<h2 id="next-steps"><a class="header" href="#next-steps">Next steps</a></h2>
<p>➡️ Now that you can create and update records, <a href="./Components.html"><strong>connect them to React components</strong></a></p>
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