95 lines
3.3 KiB
Markdown
95 lines
3.3 KiB
Markdown
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#Notes
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##Write
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Access a child from a root (db) reference:
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rootRef.child('users/mchen/name');
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Save a new user to the db:
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var usersRef = ref.child("users");
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usersRef.set({
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alanisawesome: {
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date_of_birth: "June 23, 1912",
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full_name: "Alan Turing"
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},
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gracehop: {
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date_of_birth: "December 9, 1906",
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full_name: "Grace Hopper"
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}
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});
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Flatten all data otherwise we are retrieving all children.
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Check if we have a member of a group which could be used to check if we have a GitHub user stored in the db:
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// see if Mary is in the 'alpha' group
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var ref = new Firebase("https://docs-examples.firebaseio.com/web/org/users/mchen/groups/alpha");
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ref.once('value', function(snap) {
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var result = snap.val() === null? 'is not' : 'is';
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console.log('Mary ' + result + ' a member of alpha group');
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});
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##Read
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The following should get triggered everytime we add a new repo to our list, updating our local (Ractive) ref. It gets called for every existing member too.
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// Get a reference to our posts
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var postsRef = new Firebase("https://docs-examples.firebaseio.com/web/saving-data/fireblog/posts");
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// Retrieve new posts as they are added to Firebase
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postsRef.on('child_added', function (snapshot) {
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var newPost = snapshot.val();
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console.log("Author: " + newPost.author);
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console.log("Title: " + newPost.title);
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});
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Changes can be monitored like the following. This should work even in offline mode so we should not be changing our local state but Firebase state which calls us back with the changes.
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// Get a reference to our posts
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var postsRef = new Firebase("https://docs-examples.firebaseio.com/web/saving-data/fireblog/posts");
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// Get the data on a post that has changed
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postsRef.on('child_changed', function (snapshot) {
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var changedPost = snapshot.val();
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console.log('The updated post title is ' + changedPost.title);
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});
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When we remove a repo:
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// Get a reference to our posts
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var postsRef = new Firebase("https://docs-examples.firebaseio.com/web/saving-data/fireblog/posts");
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// Get the data on a post that has been removed
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postsRef.on('child_removed', function (snapshot) {
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var deletedPost = snapshot.val();
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console.log('The blog post titled' + deletedPost.title + ' has been deleted');
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});
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##Security
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Write new users, do not update them, but allow delete.
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// we can write as long as old data or new data does not exist
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// in other words, if this is a delete or a create, but not an update
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".write": "!data.exists() || !newData.exists()"
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Accessing dynamic paths in the rules can be done using a `$` prefix. This serves as a wild card, and stores the value of that key for use inside the rules declarations:
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{
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"rules": {
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"rooms": {
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// this rule applies to any child of /rooms/, the key for each room id
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// is stored inside $room_id variable for reference
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"$room_id": {
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"topic": {
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// the room's topic can be changed if the room id has "public" in it
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".write": "$room_id.contains('public')"
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}
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}
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}
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}
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}
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[User-based rules](https://www.firebase.com/docs/web/guide/user-security.html).
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