Drupal 7, #states, and mutually exclusive checkboxes

This post will be a bit techy. I confronted and solved a minor problem yesterday, and in the spirit of the internet, thought I’d share the solution, in case anyone else tries something similar.

This is about Drupal forms, and specifically within forms, the #states capability, which is a way that form designers can tell Drupal to do jQuery magic things on the form elements, enabling or disabling some of them based on the state or value of others.

The typical example is a checkbox, that when checked, will either enable (css ‘disabled: false’) or make visible (css ‘display: block’) a dependent textbox. Simple enough, right? and for that kind of simple case, it works well.

Drupal’s Forms API is described here, and the related
drupal_process_states here.

This is what it looks like to configure a Form in Drupal:

That says, show the textfield only when the referenced checkbox is checked. The reference to the checkbox is with a jQuery selector. This one works, really straightforward. And, the state is managed by Drupal in both directions. When the referenced checkbox is checked, then the textfield is visible. When the referenced checkbox is unchecked, then the textfield becomes not visible.

But what if you want a set of mutually exclusive checkboxes?

Mutually Exclusive Checkboxes

One approach is to just use the above model, and have each checkbox depend on the other. In other words, something like this:

This will not work. The reason this does not work, is that the state is managed by drupal in both directions. When checkbox #1 is checked, then checkbox #2 becomes unchecked. Which means checkbox #1 gets checked. Which means checkbox #2 becomes unchecked. And if you turn on the Firebug debugger, you can see the logical loop going round and round, endlessly.

There was an approach described here that suggested using two conditions in the array. But that didn’t work for me; I still had the endless loop. After fiddling with this for an hour, searching around for hints, I decided to just do it myself with my own jQuery. The logic was simple to write. And, I didn’t want to fight the Drupal Forms API any longer.

So here’s the solution. Include this JavaScript in your module:

As you can see, it registers a ‘change’ hook for a specially-marked checkbox. And when the checkbox is affirmatively checked, it unchecks the other checkbox. When the checkbox is unchecked, it does nothing.

How does that JS get loaded? In the Drupal module code, do this:

And finally, how do we set up the checkboxes in the Forms API? Like this:

And that gets the desired behavior: It is possible for zero or one of those checkboxes to be checked, but not both.

It took more time to write this post than it took to build the solution shown here! And of course I never did manage to figure out how to do the same just using the Forms API. This is an example of an API, the Forms API in Drupal, that does some things well, and this one thing….? Not so well. Much easier to just jump out and solve it this way.

Maybe this will help some one else!

By the way, this is included in a Drupal module that allows administrators to verify / validate user registration.



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Bryan Kirshner on Passing the Digital Strategy Laugh Test

Bryan Kirschner of Apigee on what it takes for a CEO to pass the laugh test when it comes to digital strategy.

He proposes a handful of metrics that CEOs should be managing; and says that observers should judge CEOs on their progress on these metrics.

Makes a lot of sense to me.



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Google Guava – sweet and succulent

I have a bit of java code that handles JWT. It generates a MACVerifier and then uses that to verify a signature. Someone commented that it was taking more time than they expected. I didn’t see a ton of opportunity for optimization, but I thought I might wrap the generation of the MACVerifier in a cache.

At first I tried EHCache. EHCache is the gold standard as far as Java caching. There are sooo many options, and there is sooo much flexibility. Write through caches, read-through caches, caches with persistence that is configurable in ways you had not imagined you needed. Java Attributes to add caching to servlets or JAX-RS. EHCache has it all.

Do One Thing Well

So I figured it would be a safe choice. But after a little bit of fiddling with it, I decided EHCache was too much. To me, EHCache violates the “do one thing well” principle of design, or if you like, the Single responsibility principle (As applied to the module, if not a particular class), or, just unsatisfying documentation which is a common problem even among “successful” open source projects.

Why is there a CacheManager? What if I create a Cache and don’t register it with a CacheManager – what happens? What do I lose? Why do I want a CacheManager? Why are there names for both managers and caches? What would happen if I registered a Cache with multiple managers? What if I don’t want persistence? What if the Cache itself goes out of scope – will it be garbage collected?

I couldn’t find ready answers to these questions and the whole experience left me lacking confidence whether the cache would do the right thing for me. In the end I concluded that EHCache was more, much more than I needed, and would require more time than I wanted to invest, to get a cache. I just wanted a simple in-memory Cache in Java with TTL support (where TTL also implies time-since-last-access or time-to-idle). And what do you know! Google Guava provides that!

Guava

Goooooooooogle

At first it was unclear how to best exploit it. But a little reading showed me that Guava has a clever design that allows the cache itself to load items into it. I don’t need to write MY code to check for existence, and then create the thing, and then put it into the cache. Guava has a LoadingCache that does all this for me. I just call cache.get() and if the item is present, it is dispensed. If it is not in the cache, then the cache loads it and gives it to me. Read-Through cache loveliness. So simple and easy.

This is my code to create the cache:

And to use the cache, I just call cache.get(). Really slick. Thanks, Google!



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restclient.el – sending API Requests directly from within Emacs

Hey, something new! (to me!) the restclient.el library, for emacs. I tried it. I like it. I recommend it.

What does it do? Allows you to send REST requests (really just http requests) right from emacs, interactively. And then pretty-prints the results if possible (if XML or JSON or image). It includes a simple text mode that allows you to define a set of requests and some variables that can be used in those requests. The whole thing is simple, easy, handy.
Activate it with C-c C-c

Separately, I have a library that reads .netrc files from within elisp. It’s a natural complement to restclient.el , for API endpoints that require HTTP Basic authentication. That covers lots of API endpoints, including OAuth token dispensaries that require the client_id and client_secret to be passed in as an HTTP Basic authentication header. Here’s a simple example use:

Really nice. How did I not know about this elisp library?

One problem I had when using it: The restclient.el helpfully uses a function json-pretty-print-buffer to pretty-print the buffer containing the response, if the content-type of the response is application/json.

I don’t know that function, and it wasn’t defined on my emacs. This led to a runtime error, and a json buffer that was hard for me to visually parse.

But my emacs does have the similarly named json-prettify-buffer. So I used the following gist to get the restclient to succeed in its pretty-printing efforts.

The restclient.el module is not a huge thing, but it’s nice for us emacs people. I know about Postman, and use it. I know about Paw (but don’t use it). I know and use Fiddler. I am a big fan of curl, and someitmes curlish. This is a nice additional tool for the toolbox.  Really handy.

Thanks, Jake McCrary, for writing up your experience with Emacs and restclient.el; your blog post is how I discovered it.  And thanks of course to Pavel Kurnosov, the original author of the restclient.el library. Thanks for sharing.

EDIT – I made a change in restclient.el to fix an issue that causes an extra unintended newline to be appended to the last form parameter. This issue cost me about 90 minutes of debugging my JWT verification code, bummer! My change just trims trailing newlines from the entity being sent. This will be a problem for you if you want to send an entity that ends in several newlines. Find my fixed restclient.el here .



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Webinar on OpenID Connect and JWT in Apigee Edge, featuring yours truly

Here’s the replay of the Webinar, on OpenID Connect and JWT that I did with Vinit Mehta a week ago or so.

It’s about 45 minutes long.

If you have questions, you can post them to The Apigee Community



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letsencrypt and NearlyFreeSpeech

I’ve been running this site on nearlyfreespeech for some time now.

Last week I created a cert using the tools and service made available by letsencrypt.org, and then configured my NFS server to use it. It was pretty easy, but not documented. I’ll share here what I did to make it work.

I am able to SSH into the nearlyfreespeech server. I can also perform a git clone from that server to get the letsencrypt tools. But when I ran the letsencrypt-auto tool from the server, it didn’t do what I wanted it to do. This was my first time with the tool, and I’m unfamiliar with the options, so maybe it was just pilot error.

In any case, I solved it by running the tool on my Mac OSX machine and transferring the generated PEM files to the server.

  1. I ran git clone on my local workstation (Mac OSX)
  2. from there, I ran the letsencrypt tool with these options:
    ./letsencrypt-auto certonly  --manual  \
       -d www.dinochiesa.net -d dinochiesa.net \
       --email dpchiesa@hotmail.com
    
  3. follow the instructions. I needed to create endpoints on my NFS server that responded with specific values.
  4. when that completed, I had the cert and keys in PEM format. I then copied them to /home/protected/ssl on the NFS server
  5. opened a service ticket on NFS as per This FAQ
  6. a couple hours later, the NFS people had completed the SSL config for me

Maybe this will help someone else.

It’s possible that I could have used the –manual option on the NFS Server, and avoided the need to transfer files. Not sure. If anyone else has done this, I’d like to know. I will need to renew my certs every couple months.

I really pleased about the letsencrypt service. I hope it gets used widely.



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