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I am trying to put logic in a css-width in a data-link in jsViews. The two following approaches did not work: 

{{for Items}}
    ...
    <td id="show-keys" data-link="css-width{~root.ShowKeys ? '200px' : '400px'}">

or 

{{for Items}}
    ...
    <td id="show-keys" data-link="css-width{:~keysWidth()}">
...

<script type="text/javascript">
    ...
    var app = {
        ...
        helpers: {
            showKeys: function () {
                //debugging shows that this never gets fired
                return app.ShowKeys ? '400px' : '100px';
            }

How do I appropiatly base a css-value on a property so that it changes dynamically?

neo post modern
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2 Answers2

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At a glance here, I notice two things;

  1. For the second setup, I wouldn't expect that to work as written... your helper function is called showKeys, but in the template you are calling a function called keysWidth... maybe that was just a transcription mistake, but it definitely won't work like that. Change the names so they match (case-sensitive, as always in JS).

  2. Make sure your helpers are actually getting loaded... e.g. $.helpers({helperfunction: function() {...}}) ... sometimes that can cause issues.

BKimmel
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Here is a jsfiddle that shows a few variants: http://jsfiddle.net/BorisMoore/GZPvZ/

Your first expression missing a :

data-link="css-width{~root.ShowKeys ? '200px' : '400px'}"

should be 

data-link="css-width{:~root.ShowKeys ? '200px' : '400px'}"

For the second approach, using a helper, apart from the naming of the helper (I think you meant it to be keysWidth - as @BKimmel points out) - you need to declare the fact that it is a computed observable with a dependency on ~root.showKeys - which you do like this:

function keysWidth() {
    return app.showKeys ? '400px' : '100px';
}

keysWidth.depends = "~root.showKeys"; // or you can write ... = [app, "showKeys"]

Alternatively you can not declare the dependency, but pass it in as an argument:

data-link="css-width{:~keysWidth3(~root.showKeys)}"

Helpers can be declared globally, or passed in with the link call.

See the jsfiddle for details...

Update: There are now some new samples that cover CSS and class binding. There is a tutorial sequence on data-linking, which includes this page on data-linking class, this on on toggling class, and this one on linking to CSS attributes.

BorisMoore
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