@rikishi/watermelondb
Version:
Build powerful React Native and React web apps that scale from hundreds to tens of thousands of records and remain fast
344 lines (252 loc) • 19.2 kB
HTML
<html lang="en" class="sidebar-visible no-js light">
<head>
<!-- Book generated using mdBook -->
<meta charset="UTF-8">
<title>Flow - WatermelonDB documentation</title>
<!-- Custom HTML head -->
<meta content="text/html; charset=utf-8" http-equiv="Content-Type">
<meta name="description" content="">
<meta name="viewport" content="width=device-width, initial-scale=1">
<meta name="theme-color" content="#ffffff" />
<link rel="icon" href="../favicon.svg">
<link rel="shortcut icon" href="../favicon.png">
<link rel="stylesheet" href="../css/variables.css">
<link rel="stylesheet" href="../css/general.css">
<link rel="stylesheet" href="../css/chrome.css">
<link rel="stylesheet" href="../css/print.css" media="print">
<!-- Fonts -->
<link rel="stylesheet" href="../FontAwesome/css/font-awesome.css">
<link rel="stylesheet" href="../fonts/fonts.css">
<!-- Highlight.js Stylesheets -->
<link rel="stylesheet" href="../highlight.css">
<link rel="stylesheet" href="../tomorrow-night.css">
<link rel="stylesheet" href="../ayu-highlight.css">
<!-- Custom theme stylesheets -->
</head>
<body>
<!-- Provide site root to javascript -->
<script type="text/javascript">
var path_to_root = "../";
var default_theme = window.matchMedia("(prefers-color-scheme: dark)").matches ? "navy" : "light";
</script>
<!-- Work around some values being stored in localStorage wrapped in quotes -->
<script type="text/javascript">
try {
var theme = localStorage.getItem('mdbook-theme');
var sidebar = localStorage.getItem('mdbook-sidebar');
if (theme.startsWith('"') && theme.endsWith('"')) {
localStorage.setItem('mdbook-theme', theme.slice(1, theme.length - 1));
}
if (sidebar.startsWith('"') && sidebar.endsWith('"')) {
localStorage.setItem('mdbook-sidebar', sidebar.slice(1, sidebar.length - 1));
}
} catch (e) { }
</script>
<!-- Set the theme before any content is loaded, prevents flash -->
<script type="text/javascript">
var theme;
try { theme = localStorage.getItem('mdbook-theme'); } catch(e) { }
if (theme === null || theme === undefined) { theme = default_theme; }
var html = document.querySelector('html');
html.classList.remove('no-js')
html.classList.remove('light')
html.classList.add(theme);
html.classList.add('js');
</script>
<!-- Hide / unhide sidebar before it is displayed -->
<script type="text/javascript">
var html = document.querySelector('html');
var sidebar = 'hidden';
if (document.body.clientWidth >= 1080) {
try { sidebar = localStorage.getItem('mdbook-sidebar'); } catch(e) { }
sidebar = sidebar || 'visible';
}
html.classList.remove('sidebar-visible');
html.classList.add("sidebar-" + sidebar);
</script>
<nav id="sidebar" class="sidebar" aria-label="Table of contents">
<div class="sidebar-scrollbox">
<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"><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" class="active"><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>
</div>
<div id="sidebar-resize-handle" class="sidebar-resize-handle"></div>
</nav>
<div id="page-wrapper" class="page-wrapper">
<div class="page">
<div id="menu-bar-hover-placeholder"></div>
<div id="menu-bar" class="menu-bar sticky bordered">
<div class="left-buttons">
<button id="sidebar-toggle" class="icon-button" type="button" title="Toggle Table of Contents" aria-label="Toggle Table of Contents" aria-controls="sidebar">
<i class="fa fa-bars"></i>
</button>
<button id="theme-toggle" class="icon-button" type="button" title="Change theme" aria-label="Change theme" aria-haspopup="true" aria-expanded="false" aria-controls="theme-list">
<i class="fa fa-paint-brush"></i>
</button>
<ul id="theme-list" class="theme-popup" aria-label="Themes" role="menu">
<li role="none"><button role="menuitem" class="theme" id="light">Light (default)</button></li>
<li role="none"><button role="menuitem" class="theme" id="rust">Rust</button></li>
<li role="none"><button role="menuitem" class="theme" id="coal">Coal</button></li>
<li role="none"><button role="menuitem" class="theme" id="navy">Navy</button></li>
<li role="none"><button role="menuitem" class="theme" id="ayu">Ayu</button></li>
</ul>
<button id="search-toggle" class="icon-button" type="button" title="Search. (Shortkey: s)" aria-label="Toggle Searchbar" aria-expanded="false" aria-keyshortcuts="S" aria-controls="searchbar">
<i class="fa fa-search"></i>
</button>
</div>
<h1 class="menu-title">WatermelonDB documentation</h1>
<div class="right-buttons">
<a href="../print.html" title="Print this book" aria-label="Print this book">
<i id="print-button" class="fa fa-print"></i>
</a>
</div>
</div>
<div id="search-wrapper" class="hidden">
<form id="searchbar-outer" class="searchbar-outer">
<input type="search" name="search" id="searchbar" name="searchbar" placeholder="Search this book ..." aria-controls="searchresults-outer" aria-describedby="searchresults-header">
</form>
<div id="searchresults-outer" class="searchresults-outer hidden">
<div id="searchresults-header" class="searchresults-header"></div>
<ul id="searchresults">
</ul>
</div>
</div>
<!-- Apply ARIA attributes after the sidebar and the sidebar toggle button are added to the DOM -->
<script type="text/javascript">
document.getElementById('sidebar-toggle').setAttribute('aria-expanded', sidebar === 'visible');
document.getElementById('sidebar').setAttribute('aria-hidden', sidebar !== 'visible');
Array.from(document.querySelectorAll('#sidebar a')).forEach(function(link) {
link.setAttribute('tabIndex', sidebar === 'visible' ? 0 : -1);
});
</script>
<div id="content" class="content">
<main>
<h1 id="watermelon--flow"><a class="header" href="#watermelon--flow">Watermelon ❤️ Flow</a></h1>
<p>Watermelon was developed with <a href="https://flow.org">Flow</a> in mind.</p>
<p>If you're a Flow user yourself (and we highly recommend it!), here's some things you need to keep in mind:</p>
<h2 id="setup"><a class="header" href="#setup">Setup</a></h2>
<p>Add this to your <code>.flowconfig</code> file so that Flow can see Watermelon's types.</p>
<pre><code class="language-ini">[options]
module.name_mapper='^@rikishi/watermelondb\(.*\)$' -> '<PROJECT_ROOT>/node_modules/@rikishi/watermelondb/src\1'
</code></pre>
<p>Note that this won't work if you put the entire <code>node_modules/</code> folder under the <code>[ignore]</code> section. In that case, change it to only ignore the specific node modules that throw errors in your app, so that Flow can scan Watermelon files.</p>
<h2 id="tables-and-columns"><a class="header" href="#tables-and-columns">Tables and columns</a></h2>
<p>Table and column names are <strong>opaque types</strong> in Flow.</p>
<p>So if you try to use simple strings, like so:</p>
<pre><code class="language-js">class Comment extends Model {
static table = 'comments'
@text('body') body
}
</code></pre>
<p>You'll get errors, because you're passing <code>'comments'</code> (a <code>string</code>) where <code>TableName<Comment></code> is expected, and <code>'body'</code> (again, a <code>string</code>) where <code>ColumnName</code> is expected.</p>
<p>When using Watermelon with Flow, you must pre-define all your table and column names in one place, then only use those symbols (and not strings) in all other places.</p>
<p>We recommend defining symbols like this:</p>
<pre><code class="language-js">// File: model/schema.js
// @flow
import { tableName, columnName, type TableName, appSchema, tableSchema } from '@rikishi/watermelondb'
import type Comment from './Comment.js'
export const Tables = {
comments: (tableName('comments'): TableName<Comment>),
// ...
}
export const Columns = {
comments: {
body: columnName('body'),
// ...
}
}
export const appSchema = appSchema({
version: 1,
tables: [
tableSchema({
name: Tables.comments,
columns: [
{ name: Columns.comments.body, type: 'string' },
],
}),
// ...
]
})
</code></pre>
<p>And then using them like so:</p>
<pre><code class="language-js">// File: model/Comment.js
// @flow
import { Model } from '@rikishi/watermelondb'
import { text } from '@rikishi/watermelondb/decorators'
import { Tables, Columns } from './schema.js'
const Column = Columns.comments
export default class Comment extends Model {
static table = Tables.comments
@text(Column.body) body: string
}
</code></pre>
<h3 id="but-isnt-that-a-lot-of-boilerplate"><a class="header" href="#but-isnt-that-a-lot-of-boilerplate">But isn't that a lot of boilerplate?</a></h3>
<p>Yes, it looks more boilerplate'y than the non-Flow examples, however:</p>
<ul>
<li>you're protected from typos — strings are defined once</li>
<li>easier refactoring — you only change column name in one place</li>
<li>no orphan columns or tables — no way to accidentally refer to a column or table that was removed from the schema</li>
<li><code>TableName</code> is typed with the model class it refers to, which allows Flow to find other mistakes in your code</li>
</ul>
<p>In general, we find that untyped string constants lead to bugs, and defining typed constants is a good practice.</p>
<h3 id="associations"><a class="header" href="#associations">associations</a></h3>
<p>When using Flow, you define model associations like this:</p>
<pre><code class="language-js">import { Model, associations } from '@rikishi/watermelondb'
import { Tables, Columns } from './schema.js'
const Column = Columns.posts
class Post extends Model {
static table = Tables.posts
static associations = associations(
[Tables.comments, { type: 'has_many', foreignKey: Columns.comments.postId }],
[Tables.users, { type: 'belongs_to', key: Column.authorId }],
)
}
</code></pre>
<h2 id="common-types"><a class="header" href="#common-types">Common types</a></h2>
<p>Many types are tagged with the model class the type refers to:</p>
<pre><code class="language-js">TableName<Post> // a table name referring to posts
Collection<Post> // the Collection for posts
Relation<Comment> // a relation that can fetch a Comment
Relation<?Comment> // a relation that can fetch a Comment or `null`
Query<Comment> // a query that can fetch many Comments
</code></pre>
<p>Always mark the type of model fields. Remember to include <code>?</code> if the underlying table column is optional. Flow can't check if model fields match the schema or if they match the decorator's signature.</p>
<pre><code class="language-js">@text(Column.body) body: string
@date(Column.createdAt) createdAt: Date
@date(Column.archivedAt) archivedAt: ?Date
</code></pre>
<p>If you need to refer to an ID of a record, always use the <code>RecordId</code> type alias, not <code>string</code> (they're the same, but the former is self-documenting).</p>
<p>If you ever access the record's raw data (DON'T do that unless you <em>really</em> know what you're doing), use <code>DirtyRaw</code> to refer to raw data from external sources (database, server), and <code>RawRecord</code> after it was passed through <code>sanitizedRaw</code>.</p>
</main>
<nav class="nav-wrapper" aria-label="Page navigation">
<!-- Mobile navigation buttons -->
<a rel="prev" href="../Advanced/AdvancedFields.html" class="mobile-nav-chapters previous" title="Previous chapter" aria-label="Previous chapter" aria-keyshortcuts="Left">
<i class="fa fa-angle-left"></i>
</a>
<a rel="next" href="../Advanced/LocalStorage.html" class="mobile-nav-chapters next" title="Next chapter" aria-label="Next chapter" aria-keyshortcuts="Right">
<i class="fa fa-angle-right"></i>
</a>
<div style="clear: both"></div>
</nav>
</div>
</div>
<nav class="nav-wide-wrapper" aria-label="Page navigation">
<a rel="prev" href="../Advanced/AdvancedFields.html" class="nav-chapters previous" title="Previous chapter" aria-label="Previous chapter" aria-keyshortcuts="Left">
<i class="fa fa-angle-left"></i>
</a>
<a rel="next" href="../Advanced/LocalStorage.html" class="nav-chapters next" title="Next chapter" aria-label="Next chapter" aria-keyshortcuts="Right">
<i class="fa fa-angle-right"></i>
</a>
</nav>
</div>
<script type="text/javascript">
window.playground_copyable = true;
</script>
<script src="../elasticlunr.min.js" type="text/javascript" charset="utf-8"></script>
<script src="../mark.min.js" type="text/javascript" charset="utf-8"></script>
<script src="../searcher.js" type="text/javascript" charset="utf-8"></script>
<script src="../clipboard.min.js" type="text/javascript" charset="utf-8"></script>
<script src="../highlight.js" type="text/javascript" charset="utf-8"></script>
<script src="../book.js" type="text/javascript" charset="utf-8"></script>
<!-- Custom JS scripts -->
</body>
</html>