RemoteStorage.BaseClient

Provides a high-level interface to access data below a given root path.

A BaseClient deals with three types of data: folders, objects and files.

getListing returns a mapping of all items within a folder.  Items that end with a forward slash (“/”) are child folders.  For instance: { ‘folder/’: true, ‘document.txt’: true }

getObject / storeObject operate on JSON objects.  Each object has a type.

getFile / storeFile operates on files.  Each file has a MIME type.

remove operates on either objects or files (but not folders, folders are created and removed implictly).

Summary
RemoteStorage.BaseClientProvides a high-level interface to access data below a given root path.
Properties
storageThe RemoteStorage instance this BaseClient operates on.
baseBase path this BaseClient operates on.
schemasContains schema objects of all types known to the BaseClient instance
Events
changeEmitted when a node changes
Functions
scopeReturns a new BaseClient operating on a subpath of the current base path.
getListingGet a list of child nodes below a given path.
getAllGet all objects directly below a given path.
getFileGet the file at the given path.
storeFileStore raw data at a given path.
getObjectGet a JSON object from given path.
storeObjectStore object at given path.
removeRemove node at given path from storage.
getItemURLRetrieve full URL of item
RS#scopeReturns a new <RS.BaseClient> scoped to the given path.
declareTypeDeclare a remoteStorage object type using a JSON schema.

Properties

storage

The RemoteStorage instance this BaseClient operates on.

base

Base path this BaseClient operates on.

For the module’s privateClient this would be /<moduleName>/, for the corresponding publicClient /public/<moduleName>/.

schemas

Contains schema objects of all types known to the BaseClient instance

Events

change

Emitted when a node changes

Arguments

eventEvent object containing information about the changed node
{
   path: path, // Absolute path of the changed node, from the storage root
   relativePath: relativePath, // Path of the changed node, relative to this baseclient's scope root
   origin: 'window', 'local', 'remote', or 'conflict' // emitted by user action within the app, local data store, remote sync, or versioning conflicts
   oldValue: oldBody, // Old body of the changed node (local version in conflicts; undefined if creation)
   newValue: newBody, // New body of the changed node (remote version in conflicts; undefined if deletion)
   lastCommonValue: lastCommonValue, //most recent known common ancestor body of 'yours' and 'theirs' in case of conflict
   oldContentType: oldContentType, // Old contentType of the changed node ('yours' for conflicts; undefined if creation)
   newContentType: newContentType, // New contentType of the changed node ('theirs' for conflicts; undefined if deletion)
   lastCommonContentType: lastCommonContentType // Most recent known common ancestor contentType of 'yours' and 'theirs' in case of conflict
 }

Example of an event with origin ‘local’ (fired on page load)

{
   path: '/public/design/color.txt',
   relativePath: 'color.txt',
   origin: 'local',
   oldValue: undefined,
   newValue: 'white',
   oldContentType: undefined,
   newContentType: 'text/plain'
 }

Example of a conflict

Say you changed ‘color.txt’ from ‘white’ to ‘blue’; if you have set `RemoteStorage.config.changeEvents.window` to `true`, then you will receive:

{
   path: '/public/design/color.txt',
   relativePath: 'color.txt',
   origin: 'window',
   oldValue: 'white',
   newValue: 'blue',
   oldContentType: 'text/plain',
   newContentType: 'text/plain'
 }

But when this change is pushed out by asynchronous synchronization, this change may rejected by the server, if the remote version has in the meantime changed from ‘white’ to for instance ‘red’; this will then lead to a change event with origin ‘conflict’ (usually a few seconds after the event with origin ‘window’, if you had that activated).  Note that since you already changed it from ‘white’ to ‘blue’ in the local version a few seconds ago, `oldValue` is now your local value of ‘blue’:

{
   path: '/public/design/color.txt',
   relativePath: 'color.txt',
   origin: 'conflict',
   oldValue: 'blue',
   newValue: 'red',
   lastCommonValue: 'white',
   oldContentType: 'text/plain,
   newContentType: 'text/plain'
   lastCommonContentType: 'text/plain'
 }

In practice, you should always redraw your views to display the content of the `newValue` field when a change event is received, regardless of its origin.  Events with origin ‘local’ are fired conveniently during the page load, so that you can fill your views when the page loads.  Events with origin ‘window’ are fired whenever you change a value by calling a method on the baseClient; these are disabled by default.  Events with origin ‘remote’ are fired when remote changes are discovered during sync (only for caching startegies ‘SEEN’ and ‘ALL’).  Events with origin ‘conflict’ are fired when a conflict occurs while pushing out your local changes to the remote store in asynchronous synchronization (see example above).

Functions

scope

scope: function(path)

Returns a new BaseClient operating on a subpath of the current base path.

getListing

getListing: function(path,
maxAge)

Get a list of child nodes below a given path.

The callback semantics of getListing are identical to those of getObject.

Parameters

pathThe path to query.  It MUST end with a forward slash.
maxAgeEither false or the maximum age of cached listing in milliseconds.  Defaults to false in anonymous mode and to 2*syncInterval in connected mode.

Returns

A promise for an object, representing child nodes.  If the maxAge requirement cannot be met because of network problems, this promise will be rejected.  If the maxAge requirement is set to false, the promise will always be fulfilled with data from the local store.

Keys ending in a forward slash represent folder nodes, while all other keys represent data nodes.

For spec versions <= 01, the data node information will contain only the item’s ETag.  For later spec versions, it will also contain the content type and -length of the item.

Example

client.getListing('', false).then(function(listing) {
  // listing is for instance:
  // {
  //   'folder/': true,
  //   'document.txt': true
  // }
});

getAll

getAll: function(path,
maxAge)

Get all objects directly below a given path.

Parameters

pathPath to the folder.
maxAgeEither false or the maximum age of cached objects in milliseconds.  Defaults to false in anonymous mode and to 2*syncInterval in connected mode.

Returns

A promise for an object in the form { path : object, ...  }. If the maxAge requirement cannot be met because of network problems, this promise will be rejected.  If the maxAge requirement is set to false, the promise will always be fulfilled with data from the local store.

For items that are not JSON-stringified objects (e.g. stored using `storeFile` instead of `storeObject`), the object’s value is filled in with `true`.

Example

client.getAll('', false).then(function(objects) {
  for (var key in objects) {
    console.log('- ' + key + ': ', objects[key]);
  }
});

getFile

getFile: function(path,
maxAge)

Get the file at the given path.  A file is raw data, as opposed to a JSON object (use getObject for that).

Except for the return value structure, getFile works exactly like getObject.

Parameters

pathSee getObject.
maxAgeEither false or the maximum age of cached file in milliseconds.  Defaults to false in anonymous mode and to 2*syncInterval in connected mode.

Returns

A promise for an object:

mimeTypeString representing the MIME Type of the document.
dataRaw data of the document (either a string or an ArrayBuffer)

If the maxAge requirement cannot be met because of network problems, this promise will be rejected.  If the maxAge requirement is set to false, the promise will always be fulfilled with data from the local store.

Example

// Display an image:
client.getFile('path/to/some/image', false).then(function(file) {
  var blob = new Blob([file.data], { type: file.mimeType });
  var targetElement = document.findElementById('my-image-element');
  targetElement.src = window.URL.createObjectURL(blob);
});

storeFile

storeFile: function(mimeType,
path,
body)

Store raw data at a given path.

Parameters

mimeTypeMIME media type of the data being stored
pathpath relative to the module root.  MAY NOT end in a forward slash.
datastring, ArrayBuffer or ArrayBufferView of raw data to store

The given mimeType will later be returned, when retrieving the data using getFile.

Example (UTF-8 data)

client.storeFile('text/html', 'index.html', '<h1>Hello World!</h1>');

Example (Binary data)

// MARKUP:
<input type="file" id="file-input">
// CODE:
var input = document.getElementById('file-input');
var file = input.files[0];
var fileReader = new FileReader();

fileReader.onload = function() {
  client.storeFile(file.type, file.name, fileReader.result);
};

fileReader.readAsArrayBuffer(file);

getObject

getObject: function(path,
maxAge)

Get a JSON object from given path.

Parameters

pathRelative path from the module root (without leading slash).
maxAgeEither false or the maximum age of cached object in milliseconds.  Defaults to false in anonymous mode and to 2*syncInterval in connected mode.

Returns

A promise for the object.  If the maxAge requirement cannot be met because of network problems, this promise will be rejected.  If the maxAge requirement is set to false, the promise will always be fulfilled with data from the local store.

Example

client.getObject('/path/to/object', false).
  then(function(object) {
    // object is either an object or null
  });

storeObject

storeObject: function(typeAlias,
path,
object)

Store object at given path.  Triggers synchronization.

Parameters

typeunique type of this object within this module.  See description below.
pathpath relative to the module root.
objectan object to be saved to the given node.  It must be serializable as JSON.

Returns

A promise to store the object.  The promise fails with a ValidationError, when validations fail.

What about the type?

A great thing about having data on the web, is to be able to link to it and rearrange it to fit the current circumstances.  To facilitate that, eventually you need to know how the data at hand is structured.  For documents on the web, this is usually done via a MIME type.  The MIME type of JSON objects however, is always application/json.  To add that extra layer of “knowing what this object is”, remoteStorage aims to use JSON-LD.  A first step in that direction, is to add a @context attribute to all JSON data put into remoteStorage.  Now that is what the type is for.

Within remoteStorage.js, @context values are built using three components

http://remotestorage.io/spec/modules/A prefix to guarantee uniqueness
the module namemodule names should be unique as well
the type given herenaming this particular kind of object within this module

In retrospect that means, that whenever you introduce a new “type” in calls to storeObject, you should make sure that once your code is in the wild, future versions of the code are compatible with the same JSON structure.

How to define types?

See declareType for examples.

remove

remove: function(path)

Remove node at given path from storage.  Triggers synchronization.

Parameters

pathPath relative to the module root.

getItemURL

getItemURL: function(path)

Retrieve full URL of item

Parameters

pathPath relative to the module root.

RS#scope

Returns a new <RS.BaseClient> scoped to the given path.

Parameters

pathRoot path of new BaseClient.

Example

var foo = remoteStorage.scope('/foo/');

// PUTs data "baz" to path /foo/bar
foo.storeFile('text/plain', 'bar', 'baz');

var something = foo.scope('something/');

// GETs listing from path /foo/something/bla/
something.getListing('bla/');

declareType

Declare a remoteStorage object type using a JSON schema.  See RemoteStorage.BaseClient.Types

TODO needs proper introduction and links to relevant classes etc
Provides a high-level interface to access data below a given root path.
scope: function(path)
Returns a new BaseClient operating on a subpath of the current base path.
Base path this BaseClient operates on.
getListing: function(path,
maxAge)
Get a list of child nodes below a given path.
getAll: function(path,
maxAge)
Get all objects directly below a given path.
getFile: function(path,
maxAge)
Get the file at the given path.
storeFile: function(mimeType,
path,
body)
Store raw data at a given path.
getObject: function(path,
maxAge)
Get a JSON object from given path.
storeObject: function(typeAlias,
path,
object)
Store object at given path.
remove: function(path)
Remove node at given path from storage.
getItemURL: function(path)
Retrieve full URL of item
Declare a remoteStorage object type using a JSON schema.
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