backbone-dynamodb

This library allows you to store Backbone models in Amazon DynamoDB. It uses dynamodb-doc to provide support for all the data types available in DynamoDB, including support for full JSON documents. These are the data types supported by this library:

• Number
• String
• Boolean
• Null
• Binary data (instances of Buffer)
• Objects (including nested objects)
• Arrays (including arrays of objects)
• Backbone Models (stored as objects)
• Backbone Collections (stored as arrays)
• Date instances (stored as strings)

Installation

Execute the following command at the root of your project:

npm install backbone-dynamodb

Alternatively, you can add backbone-dynamodb as a dependency to you application's package.json file.

AWS-SDK Configuration

backbone-dynamodb uses the AWS-SDK internally. Visit this page for details on how to configure the AWS-SDK. You can also manually configure it using the config object. For instance:

var Backbone = require( 'backbone-dynamodb' );
Backbone.DynamoDB.config.update({ region: 'us-east-1' });

If you're calling this method within your application, it must be called before calling any of the methods that send requests to DynamoDB: save, fetch, and destroy.

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Backbone.DynamoDB.Model

Backbone.DynamoDB.Model is a subclass of Backbone's Model. The following properties and methods can be overwritten according to your needs:

idAttribute

Specifies the name of the primary hash key attribute in DynamoDB. The default value is id.

hashAttribute

Specifies the name of the primary hash key attribute in DynamoDB. Important: Use hashAttribute, instead of idAttribute, if the model contains a primary range key attribute.

rangeAttribute

Specifies the name of the primary range key attribute in DynamoDB.

tableName

The exact name of the DynamoDB table to use.

urlRoot

If no tableName is given, the value of urlRoot is used to determine the name of the table. First, the slash '/' at the beginning is removed (if there one), then the first character is switched to upper case. For instance: if urlRoot is '/users', the table name would be 'Users'.

newKey( options )

Overwrite this method to dynamically generate key attribute(s). When a model is saved, this method is called if the model is new (if it doesn't have a hash and/or range key). The same options object used when calling save( options ) is passed to this method. This method must return one of the following options:

• Any value. If the model doesn't use a range attribute, and the hash attribute can be generated synchronously, this function can return any value. However, its type must match the type of the primary hash key attribute defined in DynamoDB. For instance: If the table uses a Number as the primary hash key, this function must return an integer or a float number.
• Object. If the model uses a range attribute, and the key (hash and range attributes) can be generated synchronously, this function can return an object containing the hash and/or range attributes. The type of both attributes must match the DynamoDB table definition.
• Promise (Any value). If the model doesn't use a range attribute, and the hash attribute can't be generated synchronously, this function can return a jQuery-style Promise, that when resolved it provides a value to the done callback. This has only been tested with promises provided by underscore.deferred.
• Promise (Object). If the model uses a range attribute, and the key (hash and range attributes) can't be generated synchronously, this function can return a jQuery-style Promise, that when resolved it provides an Object to the done callback. This has only been tested with promises provided by underscore.deferred.

toJSON( options )

Similar to Backbone's original toJSON method but performs the following additional tasks:

• "Picks" or "omits" attributes if the attributes pick or omit are present in options.
• Serializes all Date attributes into strings if options.serializeDates is true.
• Converts attributes that are Models or Collections into objects and arrays respectively.

When saving a model, using model.save( attributes, options ), the method toJSON is called (with the same options) to convert the model into an object before saving it. Therefore you can "pick" or "omit" the attributes to be saved to DynamoDB. For instance, user.save( null, { omit: 'password' } ) would save all attributes present in the user model except for the "password" attribute.

serializeDate( name, date )

Converts a Date instance into string.

This method is called once for each Date instance in the model's attributes, prior to saving the model to DynamoDB. The default behaviour is to call the date's toISOString method. Overwrite this method to customize how Date instances are serialized according to your needs, you might also need to overwrite deserializeDate, isSerializedDate, and/or serializedDateExp.

The serialization process is recursive, therefore this method is also called for nested Date instances.

deserializeDate( name, string )

Converts a string representation of a date into an instance of Date.

When a model is fetched from DynamoDB, this method is called once for each date attribute in the model's attributes to convert dates from their string representations into instances of Date. The default behaviour is to instantiate a Date using the provided string value (return new Date( string );). Overwrite this method to customize how date strings are deserialized according to your needs, you might also need to overwrite serializeDate, isSerializedDate, and/or serializedDateExp.

The deserialization process is recursive, therefore this method is also called for nested date values.

isSerializedDate( name, string )

Determines if a string value is a serialized date.

When a model is fetched from DynamoDB, this method is used to determine if any of the attributes are serialized dates. The default behaviour is to return true if the given string value is in an ISO8601 format, which is what the Date.toISOString method uses. Overwrite this method to customize how date strings are deserialized according to your needs, you might also need to overwrite serializeDate, deserializeDate, and/or serializedDateExp.

condition( name, operator, val1, val2 )

Generates conditions for Query or Scan requests.

It uses dynamodb-doc Condition to generate the conditions. If val1 or val2 are instances of Date, they're serialized before creating the condition.

setAttributeType( name, Constructor )

Helps you define a type for a given attribute. This helps you have nested Models/Collections. It forces the specified attribute to be an instance of the specified Constructor. Sets a listener to check if the attribute is an instance of Constructor whenever the attribute is changed. If it's not an instance of Constructor, it instantiates the Constructor (passing the current attribute's value) and sets that instance as the value of such attribute.

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Backbone.DynamoDB.Collection

Backbone.DynamoDB.Collection is a subclass of Backbone's Collection. The following properties and methods can be overwritten according to your needs:

tableName

The exact name of the DynamoDB table to use.

url

If no tableName is given, the value of url is used to determine the name of the table. First, the '/' at the beginning is removed (if there's one), then the first character is switched to upper case. For instance: if url is '/users', the table name would be 'Users'.

query( dynamoDbParams, options )

Sends a "Query" request to DynamoDB to "fetch" a collection. The first argument are the parameters to use in the query request. The second argument are the options passed to the fetch method internally.

scan( dynamoDbParams, options )

Sends a "Scan" request to DynamoDB to "fetch" a collection. The first argument are the parameters to use in the scan request. The second argument are the options passed to the fetch method internally.

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save, destroy, and fetch

When calling any of these methods:

• model.save( attributes, options )
• model.destroy( options )
• model.fetch( options )
• collection.fetch( options )

backbone-dynamodb attempts to follow Backbone's original behaviour. backbone-dynamodb supports:

• success and error callbacks passed in the options argument.
• A complete callback that is executed after success or error callbacks have been executed.
• Returns an AWS Request with a jQuery-style promise interface applied to it.
  • The callbacks attached to the promise don't receive the first argument as their callback counterparts in the options object. For instance, when calling model.fetch( options ), the options.success callback receives (model, dynamoDbItem, options) as arguments, but the done callbacks, that are attached to the returned promise, only receive (dynamoDbItem, options) as arguments.

options.context

Similar to the context setting in jQuery.ajax, setting the options.context when calling save( attributes, options ), destroy( options ), or fetch( options ), will make all callback functions to be called within the given context. In other words, the value of this, within all callbacks, will be the given options.context value.

options.complete( modelOrCollection, response )

Similar to the complete setting in jQuery.ajax, the options.complete callback, if specified, is called after either options.success or options.error have been called.

options.dynamodb

When calling save( attributes, options ), destroy( options ), or fetch( options ) the DynamoDB request body is automatically generated. You can extend the request body using the options.dynamodb. For instance, you can set the DynamoDB ConsistentRead option:

model.fetch({
	dynamodb: {
		ConsistentRead: true
	}
	// Other options here
});

AWS Response

The actual AWS response object is provided to the all callbacks as options.awsResponse, except for the model.destroy method. Callbacks used in the model.destroy method, receive the AWS response object as the first argument.

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Examples

Several examples on how to use backbone-dynamodb can be found in the examples.js file