Upon a Ship


Upon a ship bound for no port
I spied a waiter waiting widely
So I spoke to him in short
I ordered waffles of a sort,
And sat there gazing at the sea
Its breakers breaking snidely.

No waffles came that day I sailed
Though many pancakes sank the bow.
Where was the waiter whom I hailed?
I feel that he has greatly failed
To render service due somehow,
And all I am is hungry now.

Five Books for Friday #4

This week I’ve stacked my five books from smallest to largest and I’ll review them in that order. I considered looking at them from largest to smallest but that seemed psychologically demoralizing. Oh, and when I say small and large I’m referring to width and height and not thickness or number of pages. This has great importance although the reason escapes me.

  1. Walking Your Way to a Better Life by Kimiko is both an inspirational and autobiographical book about a woman who used walking and proper “mental posture” to overcome depression and build an international training business. It’s refreshing to read a book by a Japanese author because their writing rhythm and cadence is so different than western authors. Although, after a while the repitition of a single theme and the sometimes wandering narrative got to me a bit. Also, while I’m a big believer in positive self talk (it can build real neurological pathways in the brain that in turn manifest in your attitude and body) I got really tired reading about the author telling herself that she loves herself.
  2. A Unicorn in a World of Donkeys by Mia Michaels had potential (I always give potential points to unicorn references) but failed to impress. The subtitle is A Guide to Life For All the Eexceptional, Excellent Misfits. Seriously, I get the whole meaning of unincorns and donkeys but she mentioned unicorns and  glowing horns so many times I felt like I was sitting in a pink bedroom surrounded by teacups and teddy bears and a couple of giggling girls who would suddenly curse for no apparent reason. It was a little disturbing.
    “Do you stand in your uniqueness, or do you hide what makes you wonderfully weird?” Mia Michaels
    I know creatives can sometimes be overly dramatic but there’s only so much “You’re amazing and should shoot for the moon” advice I can take.  What’s worse, Michaels organized her chapters into a 12 step program.  Oddly, much of the book read as if it was written for alchoholic mythical creatures.
  3. Next up is the medium sized book In Chocolate We Trust: The Hershey Company Town Unwrapped by Peter Kurie. This was another book I had high hopes for that were never realized. I thought the book was going to be some sort of biographical history of the man, the company and the town. But in the pages I actually read (there was no way I wanted to finish this one) I felt like it was merely a blandly written institutional explanation of what a trust is, why the one that controls the Hershey company is now evil and why “Captalism is bad”. You know what, let’s just move on from this one. I’m getting depressed.
  4. Now we get to my favorite book of the week. To be perfectly honest, I’m not finished with this one yet. But that’s because I’m actually enjoying reading it. If it weren’t for this whole size of book ranking thing this one would have been first, or last. The title is The Secret Life of Pronouns and it’s written by James W. Pennebaker. The premise of the book is that the pronouns we use in our speech and our writing reveal a lot about who we are. The author and his collegues have spent years developing software that can analyze writings and make predictions about the people who wrote them. Pick up the book and at least flip through it. Maybe you won’t discover any life changing conclusions but you might gain a bit of insight into how our words betray us.
  5. The biggest book this week (6 1/4″ x 9 1/4″) is Into the Lion’s Mouth by Larry Loftis. The book is “The true story of Dusko Popov: World War II spy, patriot, and the real-life inspiration for James Bond”. The book is interesting and you can definitely see where Ian Fleming got many of the attributes for Bond. As mentioned in a former post, I’m fascinated by stories of WWII espionage so for me this book was a page turner. However, as in many historical books the documentation of the story sometimes gets in the way of the story itself.  

Well, there you go. Five more books you should either read or run from. 

Toggle Layer Visibility Using URL Parameters in Web App Builder Developer Edition

ESRI’s developer edition of their Web App Builder (WAB) is a handy stand-alone tool for creating web mapping apps. While the WAB is a tool for building an app without needing to code anything, the developer edition allows users to create their own widgets and extend current functionality or themes. Even with this capability, however, there are some situations where the pre-formed development framework just doesn’t go far enough.

This was the situation I found myself in recently when trying to use the WAB to replace our custom built web map viewer at work. Our current viewer interfaces with a few third party apps by accepting url parameters that turn on or off layers and query various layers. The WAB does allow for querying layers using url parameters but it doesn’t have the ability to toggle layers using the url method.

I searched around the internet trying to find someone who has solved this problem but never found a useable solution. ESRI provides url parameter layer visibility functionality on their ArcGIS Online platform but this hasn’t made it to the WAB Developer Edition yet. I’m not sure when or if it will.

Since layer toggling is a must-have functionality for us I decided to work up a solution myself. Thankfully, the developers at ESRI named the WAB’s url handling module mapUrlParamsHandler.js so it was pretty easy to figure out what needed to be modified.

Parameter Modeling

To fix my problem I just had to add one new function. The actual turning on and off of the layers in this function was taken care of by the WAB api. The biggest concern for me was deciding on how the parameters should be passed in the url so they would be easy to use on the client side and easy (and fast) to process on the server.

I considered using the esri ArcGIS Online model of ?layers=show:0,1,2,3 for passing in layer visibility parameters. However, this becomes very cumbersome when considering showing and hiding both layers and sublayers. It would look something like ?layers=show:0,1.0-2-5,3,4;hide:6,7 or some other cryptic looking mash of numbers and characters. I wasn’t even sure the online api accepted a hide parameter. They don’t show one in their documentation.

I then considered using two separate parameters for showing and hiding (?showLayers=1,2,3&hideLayers=1,2,3) but this just adds more complexity to the code on the back side as well as the parameters the client has to plug in. Ultimately I settled on using a single parameter called layers. But then I needed to decide how to reference those layers.

If I used a zero based index url parameter list, then if the layers in the web map ever change position, I’ll have to go in and change the url references to those layers. On the other hand, if I used the titles of the layers, it wouldn’t matter what the index position of the layer is. The name of the layer and the title would still be the same.

It’s true that the title of the layer could change too. In that case we’d still have to update the urls we’re passing in to the app. But in our situation this is less likely to happen than the positon changing. Using titles has another advantage of making it clear to the casual observer exactly what layers are being acted upon. This wouldn’t matter that much since the public isn’t going to be encouraged to pass parameters into the url. But it might be nice for us developers to know what we’re doing.

I ended up using layer titles since they’re human readable and don’t rely on positioning within the web map that drives the web app. However, I created both versions of my modifications so that someone else who wants to use layer indices can do so just as easily.

In my parameter, layers are separated by commas with layers to be shown represented by the layer title (or positive index integers) and layers to be hidden represented by layer titles with a minus(-) symbol in front of them (or negative index integers).

Toggling Sub Layers

I also wanted to be able to toggle sub layers on and off. Sublayers to be toggled will be shown by separating the parent layer from the sublayers with a colon. The sublayers themselves will be separated by semicolons.

In WAB apps, sublayers are 0 index based underneath their parent. Suppose you have an active layer called School Boundaries with a map index position of 6 and it has three sublayers for High Schools, Middle Schools and Elementary Schools. These sub layers would be indexed as 0, 1, 2.

I decided to stick with index references for the sublayers since it was easy to do so and makes sense. It’s also easier to read in and understand within the url since the parent layer is text so there’s some contrast. 

With the above model of building your url for layer toggling, you can take care of almost any layer manipulation scenario you can think of.

This would turn on the Schools layer as well as the first, second and third sublayers: 
?layers=Schools:0;1;2

This would turn off the Schools layer and deselect sublayer 0, then turn the schools back on and select sub layers five and six:
?layers=-Schools:0,Schools:5;6

Edit: Having to turn an entire layer off and then on again, just to get at the sublayer, was cumbersome. Now you can use the minus symbol in front of the layer title or the sublayer index to turn themon and off independently. For example – ?layers=Schools:-0;5;6


Multiple Params


Another problem I have with the URL parameter handling capabilities of the Web App Builder is that you can’t add multiple parameters. In other words, you can’t pass in layers to turn on and do a query on a layer at the same time. To solve that problem I just modified the main function in the module to check all url parameters rather than stopping after finding the first one.

mo.postProcessUrlParams = function(urlParams, map){
    //urlParams have been decoded.
    for(var key in urlParams){
      //Loop through the urlParams object
        if(urlParams.hasOwnProperty(key)){
          //For each parameter found, run its function
          if('layers' === key){
            toggleLayers(urlParams, map);
          }else if('extent' === key){
            setExtent(urlParams, map);
          }else if('center' === key){
            setCenter(urlParams, map);
          }else if('marker' === key){
            createMarker(urlParams, map);
          }else if('find' === key){
            sendMessageToSearch(urlParams);
          }else if('query' === key){
            queryFeature(urlParams, map);
          }
        }
    }
  };

How to Use

In order to use the modified mapUrlParamsHandler module in your WAB project you first need to download the appropriate one (index driven or title driven) from Github at https://github.com/RyanDavison/WAB_URL_Parameters. Then replace the native file located in \WebAppBuilderForArcGIS\server\apps\4\jimu.js .

If you’ve already exported your app and are hosting it on your own server just find the jimu.js folder and paste the file in there. Alternatively you could just copy the code out of the files on Github and paste it right into the native mapUlrParamsHandler.js file. That’s all you have to do to get layer toggling functionality through your url.

In the future, ESRI might enable this same functionality in the WAB Developer Edition. If they do, it’s a good bet they won’t have thhe same url structure as me. As I’m writing this, The Web App Builder is at version 2.9. So if you start using my modified code now, you might be changing your own url structures to match the ESRI api. My modifications 

If you have and questions, comments or problems feel free to leave them in the comments section below or contact me on Github.

EDIT:
When I first wrote the modification You could only turn sub layers on and off along with their parent layer. So, if you wanted to turn off sub layer 2  but turn on sub layer 3 of LayerX you would have to write

?layers=-LayerX:2,LayerX:3

It was a two-step process that was very clunky. Now, you can turn off sublayers independently. So the query above would now simply read:

?layers=LayerX:-2;3

Of course you can still turn off an entire layer like this:

?layers=-LayerX

A Powerful Image

I’m facinated with photographing power lines and poles. I love finding a series of lines that follow the natural flow of the land. Or a transmission tower against a blue morning sky. There’s something about the man-made vs nature aspect of electricity transmission that draws me to it.

That’s why I was happy to find another “powerful” subject on a hike I took over the weekend. This is a perfect example of what I’m talking about here. Unfortunately, I still haven’t found anyone else who shares my curiosity on the topic.

Five Books for Friday #3

Here we go again with five of the books I’ve been digging into over the last week. The subjects this time around are an interesting mix of projects, publishing, drawing, writing and poetry. Some weeks I find a ton of books all on the same subject I’m currently interested in. Other times it’s a random mix. Either way, I typically learn something useful and get entertained at the same time.

  1. First up is Souped Up, an Instructables.com book edited by Michael Huynh. It’s a mix of projects ranging from food to electronics and woodworking to Décor and furniture. My wife was especially thrilled with Gummy Bear Surgery which details how to create your own frankengummi monsters. This is one of those really simple time wasters that make you wonder how it could take four pages of instructions. But the ideas you get out of those four pages are pretty funny. I get more excited about reuse projects like making clocks out of old computer hard drives. I was only really interested in about a third of the projects in this book. But this kind of book is great for cherry picking.
  2. I love cartooning although I don’t get around to it nearly enough. Like most cartoonists, I dream about putting together a complete comic book someday. The Complete Guide to Self-Publishing Comics by Comfort Love and Adam Withers brings that dream one step closer. It’s not a book about drawing but more a book about the technical and business side of getting your art work into book form (printed or digital) and into the hands of your readers. The book has a lot of great tips on ideation, character development and dialogue. It also steps you through using Adobe Illustrator for layout, coloring and lots of other stuff. Finally, it talks about how to market your work after publishing to get it recognized among all the other self-published comics out there. I enjoyed the “Pro Tip” sidebars sprinkled throughout the book. This type of info is fun to read and gives you a sneak peek at real life implementations of what you’re learning.
  3. I posted a few weeks ago about doing zendoodles. I was inspired by a book my son brought back from the library and I’ve kept it since then to refer back to. Tangles: Amazing Zendoodles to Color and Draw by Abby Huff has some great patterns to get you started drawing your own doodles. You really don’t need a book like this to draw zendoodles or zentangles. The whole point is to create original designs that flow like a stream of consciousness writing. But it’s still nice to see what kinds of patterns you like and the different pen strokes that can get you there.
  4. I’m always looking for inventive ways to be more productive with my time and produce more of whatever I’m trying to do. That’s why I was intrigued by the title of How to Write a Lot by Paul J. Silva. The book’s premise boils down to disciplining yourself to sit down and write regularly. Now, I could have been frustrated that there wasn’t some magic bullet between the covers of this book but it’s refreshing to have somebody just reiterate the plain truth that you already knew. The fact is, if you want to write a lot, you have to write a lot. The book does give you more insight on the subject of course. You learn what barriers to writing a lot you might encounter. And you are introduced to motivational tools, styles and how to write certain types of works. Although this book was written primarily for academic writers, it still holds a lot of great insight no matter what your genre.
  5. I saved my favorite book for last. Alone and Not Alone is a compilation of poems by Ron Padgett. Padgett is a wonderfully accessible poet who uses humor and insight to bring everyday life onto the page. I like writing poetry in all different forms and on all different topics. But I’m very selective in the poets I actually enjoy reading. Padgett is one of those poets I actually enjoy reading. As with most poets there are a few of his selections that are just a bit too obtuse for me. But overall, his imagery, style and cadence just lead me from page to page and poem to poem. Sometimes I’ll read them out loud because I enjoy listening to the words. Highly recommended.