passing params via href element to a dynamic page

TEST page params

/**
 *  TEST page params
 *
 *  Copyright 2015 Steve Vlaminck
 *
 *  Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
 *  in compliance with the License. You may obtain a copy of the License at:
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software distributed under the License is distributed
 *  on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License
 *  for the specific language governing permissions and limitations under the License.
 *
 */
definition(
    name: "TEST page params",
    namespace: "CommunityTest",
    author: "Steve Vlaminck",
    description: "passing params via href element to a dynamic page",
    category: "",
    iconUrl: "https://s3.amazonaws.com/smartapp-icons/Convenience/Cat-Convenience.png",
    iconX2Url: "https://s3.amazonaws.com/smartapp-icons/Convenience/Cat-Convenience@2x.png",
    iconX3Url: "https://s3.amazonaws.com/smartapp-icons/Convenience/Cat-Convenience@2x.png")


// ========================================================
// PAGES
// ========================================================

preferences {
	page(name: "firstPage")
	page(name: "secondPage")
    page(name: "thirdPage")
}

def firstPage() {

	def hrefParams = [
    	foo: "bar", 
        thisIs: "totally working", 
        install: checkSomeCustomLogic(),
        nextPage: "thirdPage"
    ]
    
	dynamicPage(name: "firstPage", uninstall: true) {
    	section {        
        	href(
            	name: "toSecondPage", 
                page: "secondPage", 
                params: hrefParams, 
                description: "includes params: ${hrefParams}",
                state: hrefState()
            )
            /* The href element accepts a key of `params` and expects a `Map` as the value.
             * Anything passed in `params` will be sent along with the request but will not be persisted in any way.
             * The params will be used going to the next page but will not be available when backing out of that page.
             * This, combined with the fact that pages refresh when navigating back to them, means that your params will not be
             * available if your user hits the back button. */
        }
    }
}

def secondPage(params) {
	/* firstPage included `params` in the href element that navigated to here. 
     * You must specify some variable name in the method declaration. (I used 'params' here, but it can be any variable name you want).
     * If you do not specify a variable name, there is no way to get the params that you specified in your `href` element. */

	log.debug "params: ${params}"

	dynamicPage(name: "secondPage", uninstall: true, install: params?.install) {
    	if (params.nextPage) {
        	section {
            	href(
                	name: "toNextPage", 
                    page: params.nextPage, 
                    description: hrefState() ? "You've already been to the third page": "go checkout the third page",
                    state: hrefState()
                )
            }
        } else {
	    	section {
    	    	paragraph "There were no params included when fetching this page."
        	}
        }
    }
}

def thirdPage() {

	state.reachedThirdPage = true

	dynamicPage(name: "thirdPage") {
    	section {
        	image "https://placekitten.com/g/600/500"
        }
    }
}

// ========================================================
// HELPERS
// ========================================================


def checkSomeCustomLogic() {
	// ... 
	false
}

def hrefState() {
    /* `state: "complete"` makes the right side of the href green. 
	 * It's a great way to show the user that they've already set up some stuff on that page. 
	 * In other words, it's a great way to show state ;) 
	 * If you're using hrefs, it's a good idea to set `state` when appropriate. */
     state.reachedThirdPage ? "complete": ""
}

// ========================================================
// HANDLERS
// ========================================================


def installed() {
	log.debug "Installed with settings: ${settings}"

	initialize()
}

def updated() {
	log.debug "Updated with settings: ${settings}"

	unsubscribe()
	initialize()
}

def initialize() {
	// TODO: subscribe to attributes, devices, locations, etc.
}

// TODO: implement event handlers