Using Persistent Flash Message Library for ColdFusion - coldfusion

Question

I am trying to use a library for showing Flash Messages https://github.com/elpete/flashmessage But I am having trouble getting it working correctly. The documentation isn't that great and I am new to ColdFusion. I want to have the ability to have persistent error messages across pages. Specifically during checkout so when the user needs to go back or a validation error occurs the message will appear. According to the documentation:
The FlashMessage.cfc needs three parameters to work:
A reference to your flash storage object. This object will need
get(key) and put(key, value) methods. A config object with the
following properties: A unique flashKey name to avoid naming
conflicts. A reference to your containerTemplatePath. This is the view
that surrounds each of the individual messages. It will have
references to a flashMessages array and your messageTemplatePath. A
reference to your messageTemplatePath. This is the view that
represents a single message in FlashMessage. It will have a reference
to a single flash message. The name is chosen by you in your container
template. Create your object with your two parameters and then use it
as normal.
I am getting the error
the function getMessages has an invalid return value , can't cast null value to value of type [array]
I had this script somewhat working at one point but it seems very finicky. I believe it is my implementation of it. I am hoping someone here can help me figure out where I went wrong. Or give me some pointers because I am not sure I am even implementing it correctly.
This is What I have in my testing script:
<cfscript>
alertStorage = createObject("component", 'alert');
config = {
flashKey = "myCustomFlashKey",
containerTemplatePath = "/flashmessage/views/_templates/FlashMessageContainer.cfm",
messageTemplatePath = "/flashmessage/views/_templates/FlashMessage.cfm"
};
flash = new flashmessage.models.FlashMessage(alertStorage, config);
flash.message('blah');
flash.danger('boom');
</cfscript>
And inside of alert.cfc I have:
component {
public any function get(key) {
for(var i = 1; i < ArrayLen(session[key]); i++) {
return session[key][i];
}
}
public any function put(key, value) {
ArrayAppend(session.myCustomFlashKey, value);
return true;
}
public any function exists() {
if(structKeyExists(session,"myCustomFlashKey")) {
return true;
} else {
session.myCustomFlashKey = ArrayNew();
return false;
}
}
}
The Flash Message Component looks like this:
component name="FlashMessage" singleton {
/**
* #flashStorage.inject coldbox:flash
* #config.inject coldbox:setting:flashmessage
*/
public FlashMessage function init(any flashStorage, any config) {
instance.flashKey = arguments.config.flashKey;
singleton.flashStorage = arguments.flashStorage;
instance.containerTemplatePath = arguments.config.containerTemplatePath;
instance.messageTemplatePath = arguments.config.messageTemplatePath;
// Initialize our flash messages to an empty array if it hasn't ever been created
if (! singleton.flashStorage.exists(instance.flashKey)) {
setMessages([]);
}
return this;
}
public void function message(required string text, string type = "default") {
appendMessage({ message: arguments.text, type = arguments.type });
}
public any function onMissingMethod(required string methodName, required struct methodArgs) {
message(methodArgs[1], methodName);
}
public any function render() {
var flashMessages = getMessages();
var flashMessageTemplatePath = instance.messageTemplatePath;
savecontent variable="messagesHTML" {
include "#instance.containerTemplatePath#";
}
setMessages([]);
return messagesHTML;
}
public array function getMessages() {
return singleton.flashStorage.get(instance.flashKey, []);
}
private void function setMessages(required array messages) {
singleton.flashStorage.put(
name = instance.flashKey,
value = arguments.messages
);
}
private void function appendMessage(required struct message) {
var currentMessages = getMessages();
ArrayAppend(currentMessages, arguments.message);
setMessages(currentMessages);
}
}