Category: Cool Stuff

“Be not simply good, be good for something.”
— Henry David Thoreau

One of the things that I love about incrementally building parts is that you can obtain value from the version that you have right now, yet still leave open the possibility of adding even more value in the future. When I first set out to attempt to construct a universal form field tag, I had no idea of the ways in which that would grow, but I was able to make use of it as it was at every step along the way. The other day I had a need for field that was only required if another field contained a certain value. When I went to set that up using my latest iteration of the form field tag, I realized that the current version of the code does not support that. That’s not really a problem, though; that’s just another opportunity to create a better version!

We already have an snh-required attribute, but in the current version, it simply adds an HTML required attribute to the input element. It would seem simple enough to just replace that with an ng-required attribute instead, and we would be good to go. However, we also have the required indicator to think about — that grey/red asterisk in front of the field label. That needs to go away when something changes and the field is no longer required. But let’s keep things simple and just focus on one thing at a time. In the current version, we use an internal boolean variable called required to control what gets included in the template that we are building. We can continue to use that, keeping it boolean for false, and then making it a string for anything else. The code to do that looks like this:

var required = false;
if (attrs.snhRequired && attrs.snhRequired.toLowerCase() != 'false') {
	if (attrs.snhRequired.toLowerCase() == 'true') {
		required = 'true';
	} else {
		required = attrs.snhRequired;
	}
}

You may wonder at this point why we make it a boolean for false and a string for true, but hopefully that will reveal itself when we look at the rest of the code. The next thing that we can look at is a little snippet of code that repeats itself a few times throughout the script as it is used when building the input element for a number of different field types:

... + (required?' ng-required="' + required + '"':'') + ...

This is a conditional based on the required variable, which will resolve to true for any non-empty string, but false for the boolean value of false. If the value of required is not false, then we use that same variable, which we now know is a string, to complete the ng-required attribute value for the input element. This will work for values of ‘true’ just as easily as for values that contain some kind of complex conditional statement. This was the easy part, and all of the logic was resolved within the code that generates the template.

The required indicator is another story entirely. Since some condition can toggle the element from required to not required, that same condition needs to apply to the required indicator as well. If the value of the snh-required attribute is anything other than simply ‘true’ or false, we will have to incorporate that logic in the indicator element to determine whether or not to show the indicator image. That code now looks like this:

htmlText += "          <span id=\"status." + name + "\"";
if (required) {
	if (required == 'true') {
		htmlText += " ng-class=\"" + model + refExtra + ">''?'snh-required-filled':'snh-required'\"";
	} else {
		htmlText += " ng-class=\"(" + required + ")?(" + model + refExtra + ">''?'snh-required-filled':'snh-required'):''\"";
	}
}
htmlText += "></span>\n";

As before, the first conditional is based on the required variable, and if it is false, then we don’t do anything at all. But in this case, we also have to check to see if it is equal to the string ‘true’, because if it is, we can just do what we were doing before to make this work. If it is not, then we have to include the required condition in the rendered ng-class attribute to toggle the indicator off and on at the same time that the field requirement is being toggled off and on. When the field is not required, the indicator should just go away, and when it is required, it should be there, and it should be red if the field is empty and grey if it has a value.

That’s it for the code changes. To test it, I brought up my old friend the, form field testing widget, and then altered my textarea example to look like this:

<snh-form-field
  snh-model="c.data.textarea"
  snh-name="textarea"
  snh-label="Text Area"
  snh-type="textarea"
  snh-required="c.data.select==2"
  maxlength="20"
  snh-help="This is where the field-level help is displayed. This field should be required if Option #2 is selected above."/>

That should make the textarea field required when Option #2 is selected on the field that is now above:

… and it should not be required when anything else is chosen:

With everything looking pretty solid, I was ready to generate another Update Set and call it good. Instead, I thought maybe I would just try a few more things, just to be sure. That’s when I discovered the problem.

It’s always something. I tinkered with the last name field to make it only required if the first name value was greater than spaces, and suddenly all of the form fields that followed within that same DIV disappeared.

That’s not right. Not only is it not right, I have no idea why that is happening. If you put a greater than (‘>’) sign in the value of the snh-required attribute, anything that follows in the same DIV evaporates. I tried a number of things to fix it, and I found quite a few ways to work around it, but I was never able to actually solve the problem. I hate releasing something that has this kind of a bug in it, but since I don’t seem to posses the mental capacity required to remove the flaw at this particular moment in time, that’s what I am going to end up doing. There are work-arounds, though, so I don’t feel that bad about it. Here are some of the ones that worked for me:

• Enclose the snh-form-field tag with a DIV. Since the problem only wipes out things within the same DIV, if it is the only thing in the DIV, the problem goes away. I actually tried to do that within the template itself, but that doesn’t work; the DIV has to be outside of the tag, not part of the code that is generated by the tag.
• Encode the greater than sign. Actually, you have to double encode it, as > will not work, but > does the trick. Not my idea of an intuitive solution, but it does work. And again, I tried to do that within the template itself, but that does nothing at all.
• Don’t use a greater than sign. In my own example, I could have used snh-required=”c.data.firstName” and that would have worked just as well as snh-required=”c.data.firstName>””. Also, you can call a function that contains the greater than condition, which keeps it out of the attribute value as well.

Again, these are just work-arounds. In my mind, you shouldn’t have to do that. Hopefully, in some future version, you won’t. But if you want to play around with it the way that it is, here is the latest Update Set.

Update: There is a better (enhanced) version here (… but it still doesn’t address the > issue.)