The purpose of the Flash RAM is to allow variables to be persisted seamlessly from one request and be picked up in a subsequent request(s) by the same user. This allows you to hide implementation variables and create web flows or conversations in your ColdBox applications. So why not just use session or client variables? Well, most developers forget to clean them up and sometimes they just end up overtaking huge amounts of RAM and no clean cut definition is found for them. With Flash RAM, you have the facility already provided to you in an abstract and encapsulated format. This way, if you need to change your flows storage scope from session to client scope, the change is seamless and painless.

Every handler, plugin, interceptor, layout and view has a flash object in their variables scope already configured for usage. The entire flash RAM capabilities are encapsulated in a flash object that you can use in your entire ColdBox code. Not only that, but the ColdBox Flash object is based on an interface and you can build your own Flash RAM implementations very easily. It is extremely flexible to work on a concept of a Flash RAM object than on a storage scope directly. So future changes are easily done at the configuration level.

Our Flash Scope also can help you maintain flows or conversations between requests by using the discard() and keep() methods. This will continue to expand in our 3.X releases as we build our own conversations DSL to define programmatically wizard like or complex web conversations. Also, the ColdBox Flash RAM has the capability to not only maintain this persistence scope but it also allows you to seamlessly re-inflate these variables into the request collection or private request collection, both or none at all.

The ColdBox Flash capabilities are very flexible and you can easily create your own Flash Implementations by doing two things:

1. Create a CFC that inherits from coldbox.system.web.flash.AbstractFlashScope

2. Implement the following functions: clearFlash(), saveFlash(), flashExists(), and getFlash()

Implementable Methods

Caution It is the developer's responsibility to provide consistent storage locking and synchronizations.

All of the methods must be implemented and they have their unique purposes as you read in the description. Let's see a real life example, below you can see the flash implementation for the session scope:

/**
*********************************************************************************
* Copyright Since 2005 ColdBox Framework by Luis Majano and Ortus Solutions, Corp
* www.coldbox.org | www.luismajano.com | www.ortussolutions.com
********************************************************************************
* This flash scope is smart enough to not create unecessary session variables
* unless data is put in it.  Else, it does not abuse session.
* @author Luis Majano <lmajano@ortussolutions.com>
*/
component extends="coldbox.system.web.flash.AbstractFlashScope" accessors="true"{

    // The flash key
    property name="flashKey";

    /**
    * Constructor
    * @controller.hint ColdBox Controller
    * @defaults.hint Default flash data packet for the flash RAM object=[scope,properties,inflateToRC,inflateToPRC,autoPurge,autoSave]
    */
    function init( required controller, required struct defaults={} ){
        super.init( argumentCollection=arguments );

        variables.flashKey = "cbox_flash_scope";

        return this;
    }

    /**
    * Save the flash storage in preparing to go to the next request
    * @return SessionFlash
    */
    function saveFlash(){
        lock scope="session" type="exclusive" throwontimeout="true" timeout="20"{
            session[ variables.flashKey ] = getScope();
        }
        return this;
    }

    /**
    * Checks if the flash storage exists and IT HAS DATA to inflate.
    */
    boolean function flashExists(){
        // Check if session is defined first
        if( NOT isDefined( "session" ) ) { return false; }
        // Check if storage is set and not empty
        return ( structKeyExists( session, getFlashKey() ) AND NOT structIsEmpty( session[ getFlashKey() ] ) );
    }

    /**
    * Get the flash storage structure to inflate it.
    */
    struct function getFlash(){
        if( flashExists() ){
            lock scope="session" type="readonly" throwontimeout="true" timeout="20"{
                return session[ variables.flashKey ];
            }
        }

        return {};
    }

    /**
    * Remove the entire flash storage
    * @return SessionFlash
    */
    function removeFlash(){
        lock scope="session" type="exclusive" throwontimeout="true" timeout="20"{
             structDelete( session, getFlashKey() );
        }
        return this;
    }

}

As you can see from the implementation, it is very straightforward to create a useful session flash RAM object.

There are times where you need to store user related variables in some kind of permanent storage then relocate the user into another section of your application, be able to retrieve the data, use it and then clean it. All of these tedious operations are definitely doable but why reinvent the wheel if we can have the platform give us a tool for maintaing conversation variables across requests. The key point for Flash RAM is where will the data be stored so that it is unique per user. ColdFusion gives us several persistent scopes that we can use and we have also created several flash storages for this purpose. Since the ColdBox flash scope is based on an interface, the flash scope storage can be virtually anywhere. You will find all of these implementations in the following package: coldbox.system.web.flash. In order to choose what implementation to use in your application you need to tell the ColdBox.cfc which one to use via flash configuration structure:

Configuration

Below is a nice chart of all the keys in this configuration structure so you can alter behavior of the Flash RAM objects:

Core Flash Implementations

The included flash implementations for ColdBox are:

Configuration Properties

Each RAM implementation can also use properties in order to alter its behavior upon construction via the properties configuration struct. Below are the properties our core implementations can use:

Session Flash Settings

• none

Cluster Flash Settings

• none

Client Flash Settings

• none

Mock Flash Settings

• none

Cache Flash Settings

• cacheName : The cache provider name declared in CacheBox

There are several ways to interact with the ColdBox Flash RAM:

• Using the flash scope object (Best Practice)

• Using the persistVariables() method from the super type and ColdBox Controller

• Using the persistence arguments in the setNextEvent() method from the super type and ColdBox Controller.

All of these methods interact with the Flash RAM object but the last two methods not only place variables in the temporary storage bin but actualy serialize the data into the Flash RAM storage immediately. The first approach queues up the variables for serialization and at the end of a request it serializes the variables into the correct storage scope, thus saving precious serialization time. In the next section we will learn what all of this means.

Flash Scope Object

The flash scope object is our best practice approach as it clearly demarcates the code that the developer is using the flash scope for persistence. Any flash scope must inherit from our AbstractFlashScope and has access to several key methods that we will cover in this section. However, let's start with how the flash scope stores data:

1. The flash persistence methods are called for saving data, the data is stored in an internal temporary request bin and awaiting serialization and persistence either through relocation or termination of the request.

2. If the flash methods are called with immediate save arguments, then the data is immediately serialized and stored in the implementation's persistent storage.

3. If the flash's saveFlash() method is called then the data is immediately serialized and stored in the implementation's persistent storage.

4. If the application relocates via setNextEvent() or a request finalizes then if there is data in the request bin, it will be serialized and stored in the implementation's storage.

Caution By default the Flash RAM queues up serializations for better performance, but you can alter the behavior programmatically or via the configuration file.

Info If you use the persistVariables() method or any of the persistence arguments on the setNextEvent() method, those variables will be saved and persisted immediately.

To review the Flash Scope methods, please go to the API and look for the correct implementation or the AbstractFlashScope.

Info Please note that the majority of a Flash scope methods return itself so you can concatenate method calls. Below are the main methods that you can use to interact with the Flash RAM object:

clear()

Clears the temporary storage bin

flash.clear();

clearFlash()

Clears the persistence flash storage implementation

flash.clearFlash();

discard()

any discard([string keys=''])

Discards all or some keys from flash storage. You can use this method to implement flows.

// discard all flash variables
flash.discard();

// dicard some keys
flash.discard('userID,userKey,cardID');

exists()

boolean exists(string name)

Checks if a key exists in the flash storage

if( flash.exists('notice') ){
 // do something
}

get()

any get(string name, [any default])

Get's a value from flash storage and you can even pass a default value if it does not exist.

// Get a flash key that you know exists
cardID = flash.get("cardID");

// Render some flash content
<div class="notice">#flash.get("notice","")#</div>

getKey()

Get a list of all the objects in the temp flash scope.

Flash Keys: #structKeyList( flash.getKeys() )#

getFlash()

Get a reference to the permanent storage implementation of the flash scope.

<cfdump var="#flash.getFlash()#">

getScope()

Get the flash temp request storage used throughout a request until flashed at the end of a request.

<cfdump var="#flash.getScope()#">

isEmpty()

Check if the flash scope is empty or not

<cfif !flash.isEmpty()>
</cfif>

keep()

any keep([string keys=''])

Keep all or a single flash temp variable alive for another relocation. Usually called from interceptors or event handlers to create conversations and flows of data from event to event.

function step2(event){
    // keep variables for step 2 wizard
    flash.keep('userID,fname,lname');

    // keep al variables
    flash.keep();
}

persistRC()

any persistRC([string include=''], [string exclude=''], [boolean saveNow='false'])

Persist keys from the ColdBox request collection into flash scope. If using exclude, then it will try to persist the entire request collection but excluding certain keys. Including will only include the keys passed from the request collection.

// persist some variables that can be reinflated into the RC upon relocation
flash.persistRC(include="name,email,address");
setNextEvent('wizard.step2');

// persist all RC variables using exclusions that can be reinflated into the RC upon relocation
flash.persistRC(exclude="ouser");
setNextEvent('wizard.step2');

// persist some variables that can be reinflated into the RC upon relocation and serialize immediately
flash.persistRC(include="email,addressData",savenow=true);

put()

any put(string name, any value, [boolean saveNow='false'], [boolean keep='true'], [boolean inflateToRC=FROMConfig], [boolean inflateToPRC=FROMConfig], [boolean autoPurge=FROMConfig)

This is the main method to place data into the flash scope. You can optionally use the arguments to save the flash immediately, inflate to RC or PRC on the next request and if the data should be auto purged for you. You can also use the configuration settings to have a consistent flash experience, but you can most certainly override the defaults. By default all variables placed in flash RAM are automatically purged in the next request once they are inflated UNLESS you use the keep() methods in order to persist them longer or create flows. However, you can also use the autoPurge argument and set it to false so you can control when the variables will be removed from flash RAM. Basically a glorified ColdFusion scope that you can use.

// persist some variables that can be reinflated into the RC upon relocation
flash.put(name="userData",value=userData);
setNextEvent('wizard.step2');

// put and serialize immediately.
flash.put(name="userData",value=userData,saveNow=true);

// put and mark them to be reinflated into the PRC only
flash.put(name="userData",value=userData,inflateToRC=false,inflateToPRC=true);


// put and disable autoPurge, I will remove it when I want to!
flash.put(name="userData",value=userWizard,autoPurge=false);

putAll()

any putAll(struct map, [boolean saveNow='false'], [boolean keep='true'], [boolean inflateToRC='[runtime expression]'], [boolean inflateToPRC='[runtime expression]'], [boolean autoPurge='[runtime expression]'])

Same as the put() method but instead you pass in an entire structure of name-value pairs into the flash scope.

var map = {
    addressData = rc.address,
    userID = securityService.getUserID(),
    loggedIn = now()
};

// put all the variables in flash scope as single items
flash.putAll(map);

// Use them later
if( flash.get("loggedIn") ){

}

remove()

any remove(string name, [boolean saveNow='false'])

Remove an object from the temporary flash scope so when the flash scope is serialized it will not be serialized. If you would like to remove a key from the flash scope and make sure your changes are reflected in the persistence storage immediately, use the saveNow argument.

// mark object for removal
flash.remove('notice');

// mark object and remove immediately from flash storage
flash.remove('notice',true);

removeFlash()

Remove the entire flash storage. We recommend using the clearing methods instead.

saveFlash()

Save the flash storage immediately. This process looks at the temporary request flash scope and serializes if it needs to and persists to the correct flash storage on demand.

Info We would advice to not overuse this method as some storage scopes might have delays and serializations

flash.saveFlash();

size()

Get the number of the items in flash scope

You have #flash.size()# items in your cart!

More Examples

// handler code:
function saveForm(event){
    // save post
    flash.put("notice","Saved the form baby!");
    // relocate to another event
    setNextEvent('user.show');
}
function show(event){
    // Nothing to do with flash, inflating by flash object automatically
    event.setView('user.show');
}

// User/show.cfm template using if statements
<cfif flash.exists("notice")>
    <div class="notice">#flash.get("notice")#</div>
</cfif>

// User/show.cfm using defaults
<div class="notice">#flash.get(name="notice",defaultValue="")</div>